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Full text of "Cid mining district of Davidson County, North Carolina"

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HDRTH CAROLINA LIBRARY COMMISSION 

RALEIGH, N.C. 

NORTH CAROLINA GEOLOGICAL AND 
ECONOMIC SURVEY 

JOSEPH HYDE PRATT, STATE GEOLOGIST 

Worth Carolina State Library 

(^ "fetefglr 



tf* fa 

BULLETIN No. 22 






CID MINING DISTRICT OF DAVIDSON COUNTY 

NORTH CAROLINA 



BY 
JOSEPH E?POGUE, Jr., Ph. D. 




HALEIGH 

Edwards & Broughton Printing Co., State Printers 
1910 






GEOLOGICAL BOARD. 



Governor W. W. Kitchin, ex officio Chairman Raleigh. 

_ TT ... .Asheville 

Frank R. Hewitt 

„„ _ Wilmington. 

Hugh MacRae 

.... Edenton. 

C. S. Vann 

. . . Lumberton. 
R. D. Caldwell 

Joseph Hyde Pratt, State Geologist Cha P el HllL 



LETTEK OF TRANSMITTAL. 



CnAPEL Hill, N. C., June 1, 1910. 
To His Excellency, Hon. W. W. Kitciiin, 

Governor of North Carolina. 
Sir: A report has just been completed by Dr. Joseph E. Pogue, 
Jr., on The Cid Mining District of Davidson County, North Caro- 
lina, and I would recommend that this report be published as Bulle- 
tin 22 of the publications of the North Carolina Geological and Eco- 
nomic Survey. 

This report covers a geological investigation of the Cid mining 
region and is a continuation of the study of the geological formations 
of Piedmont North Carolina that was begun in the Gold Hill Min- 
ing District, the results of which were published in Bulletin 21. 

Yours respectfully, 

Joseph Hyde Pratt, 

State Geologist. 



421 H4 



TABLE OF CONTENTS. 



PAGE. 

Introduction 13 

Chapter I: Geography and History 15 

Geographical Sketch of the Cid Mining District 15 

Location 15 

Topography. 16 

Drainage 16 

Soil 16 

Climate 16 

Culture 17 

Previous geologic work 17 

Chapter II: General Geology or Field Description of the Rocks. . . 26 

Introduction 26 

Slate 27 

Acid fine tuff 28 

Acid coarse tuff 29 

Acid volcanic breccia 31 

Rhyolite 32 

Dacite 33 

Andesitic fine tuff 34 

Andesitic coarse tuff and breccia 34 

Andesite 36 

Dike Rocks 36 

Gabbro 36 

Diabase 3g 

Chapter III: A Detailed Description of the Rocks 39 

Introduction 39 

Slate ; 4q 

Macroscopic description 40 

Microscopic description 40 

Texture 41 

Chemical composition 41 

Classification 42 

Weathering 43 

The acid fine-grained tuffs 43 

Macroscopic description 44 

Microscopic description 44 

Texture 45 

Chemical composition 45 

Classification 45 

Arenaceous phase 45 

Weathering 45 

The acid coarse tuffs 46 

Macroscopic description 46 

Microscopic description 47 



CONTENTS. 

PAGE. 

... 48 
Texture ,g 

Classification „ 

Weathering . Q 

The acid volcanic breccia 

Macroscopic description 

Microscopic description 

Classification . 

Weathering ; 

Rhyolite ■ _„ 

Macroscopic description 

Microscopic description 

Texture 

Chemical composition 

Classification 

54 
Variation — 

Weathering 

Dacite 

Macroscopic description 

Microscopic description • 

Texture ^ 

Chemical composition 

Classification 

Weathering 

The basic tuffs, breccias and flows °7 

Andesitic fine tuff 

Macroscopic description 57 

Microscopic description 58 

Classification °° 

Weathering • 58 

The andesitic coarse tuffs and breccias 58 

Macroscopic description 59 

Microscopic description 59 

Texture 62 

Chemical composition 6d 

Classification • "" 

Weathering 64 

Andesite 64 

Macroscopic description 64 

Microscopic description "° 

Trachytic variation 67 

Texture 67 

Chemical composition 67 

Classification 68 

Weathering , 68 

Dike rocks 68 

Gabbro 68 

Macroscopic description 69 

Microscopic description 69 



CONTKNTS. 



PAGE. 

Texture 70 

Classification 70 

Weathering 70 

Diabase 71 

Macroscopic description 71 

Microscopic description 71 

Texture 72 

Chemical composition 73 

Classification 73 

Weathering 73 

Chapter IV: Physiography 74 

Introduction 74 

Relief 74 

Sammary 76 

Drainage 76 

Summary 78 

Physiographic history 78 

Surface configuration of the various formations 80 

Chapter V: Structure and Metamorphism 81 

Introduction 81 

Structural features 81 

Folding 81 

Mashing 84 

Jointing ' 85 

Faulting 87 

Interpretations of structure 88 

Most probable interpretation 88 

Alternate hypotheses 89 

Metamorphic features 90 

Textural change involved in mashing 90 

Mineralogic changes involved in mashing 90 

Silicification 91 

Detailed discussion of the geologic history 91 

Igneous activity ' 91 

Sedimentation 92 

Consolidation 92 

Folding and the development of schistosity, jointing, and probable 

faulting 92 

Introduction of gabbro dikes 93 

Passage of heated solutions 93 

Operation of a secondary force, inducing minor jointing 94 

Introduction of diabase dikes 94 

Weathering and erosion 94 

Summary of geologic history 95 

Thickness and age of the slate series 95 

Thickness , 95 

Age 95 



3 CONTENTS. 

PAGE. 

Chapter VI: Ores and Mines of the District 96 

Historical 

Production '• ; 

Cost of production • 97 

Present state and importance of the district 97 

Description of the mines and prospects 97 

Types of deposits 9s 

The Silver Hill type 98 

Silver Hill Mine 98 

Location 9S 

History " 

Surface features 1°1 

Underground developments 101 

Ore 102 

Assays of ore 1^3 

Equipment lu,i 

Silver Valley Mine 104 

Location 104 

History 104 

Surface features 105 

Underground development 105 

Ore 106 

Equipment ...:... ■ • • 106 

Welborn Mine 106 

Location • • 106 

History 107 

Nooe Mine 1°7 

Ida Mine 108 

Sechrist Mine 1° 8 

Baltimore Mine 108 

The Conrad Hill type 108 

Conrad Hill Mine .108 

Location ' 108 

History 109 

Surface features HO 

Underground development HI 

Ore 112 

Equipment 112 

Peters Mine H2 

Location 112 

History 112 

Surface features 112 

Underground development 113 

Ore , 113 

Equipment v 113 

Cross Mine 113 

Location 113 

History and description 113 



CONTENTS. 9 

PAGE. 

The Emmons type 115 

Emmons Mine 115 

Location "115 

History 115 

Surface features x 115 

Underground development 115 

Ore and gangue 116 

Value of the ore 117 

Equipment 117 

Cid Mine. 117 

Location 117 

History and description 117 

Ward Mine 118 

Location 118 

History 118 

Description 118 

Features of the ore deposits 118 

List of minerals 119 

Description of ore minerals 119 

Description of gangue minerals 120 

Description of the veins 120 

Paragcnesis or order of formation of the ores 122 

Ore from the Silver Hill Mines 122 

Macroscopic description * 122 

Microscopic description 122 

Ore from the Silver Valley Mine. 123 

Ore from the Emmons Mine 123 

Macroscopic description. 123 

Microscopic description. 123 

Genesis of ore deposits 124 

Solutions 124 

Source of materials 125 

Deposition of the ores 127 

Age of ore deposits 129 

Secondary enrichment 129 

Chapter VII : Summary 131 

Rocks 131 

Structure 132 

Economic geology 133 

Appendix: Bibliography of the Cid Mining District 134 



LIST OF ILLUSTRATIONS. 



PLATE. FACING PAGE. 

I. Flat Swamp Mountain from the east near Cid, Davidson County, N. C. 15 
II. A, Outcrop of coarse, acid tuff, showing its rough weathered surface 

from near Flat Swamp Ridge, Davidson County, N. C 30 

B, Narrow and elongated outcrops of the mashed acid coarse tuff east 
of Kemp Mountain, Davidson County, N. C. Similar outcrops have 
been described as resembling "cockade hats" 30 

III. A, Outcrop of the acid volcanic breccia from Flat Swamp Mountain, 

Davidson County, N. C 32 

B, Enormous outcrops of the acid volcanic breccia upon Surratt Moun- 
tain, Davidson County, N. C 32 

IV. Geological map of the Cid Mining District, showing also location of 
mines and prospects 34 

V. A, Wedge-shaped outcrops of the mashed andesite breccia a mile west 

of Three Hat Mountain, Davidson County, N. C 36 

B, Weathered surface of the andesitic breccia, showing the character- 
istic billowy or bumpy exterior, Three Hat Mountain, Davidson 
County, N. C 36 

VI. A, Typical outcrop of slate in Buddie Branch, southwest of Silver 

Hill, Davidson County, N. C 40 

B, Hand specimen of a black slate with cross bedding strikingly 

brought out on the weathered surface 40 

VII. A, Hand specimen of the acid coarse tuff. Fragments are small and 

subordinate to the dense groundmass 46 

B, Photomicrograph of an acid tuff, Davidson County, N. C. 30 
diameters; polarized light; showing the fragmentary character of the 

rock 46 

VIII. A, Hand specimen of the acid volcanic breccia from Flat Swamp 
Ridge. It is made up of predominant light colored, acid fragments 
over X A inch in diameter. A dark colored andesitic fragment may 

be seen in the center of the specimen 50 

B, Small boulder of the acid volcanic breccia, showing a character- 
istic spongelike surface developed on weathering 50 

IX. Photomicrograph of a fragment contained in the acid volcanic breccia, 
Davidson County, N. C. 30 diameters; ordinary light; showing 

fragmentary nature of components • 52 

B, Same in polarized light, showing the angular and shred-like outline 

of the components • • • 52 

X. A, Hand specimen of rhyolite showing flow structure made prom- 
inent by weathering, Flat Swamp Ridge, Davidson County, N. C 54 

B, Hand specimen of a very dense and highly siliceous rock, contain- 
ing abundant areas of galena, chalcopyrite and pyrite. The small 
white specks are minute aggregates of granular kaolin. The rock is 
either a silicified tuff or de vitrified rhyolite. From one mile north- 
west of the Emmons Mine, Davidson County, N. C 54 



12 



LIST OF ILLUSTRATIONS. 



PLATE. FACING PAGE. 

XI. A, Hand specimen of andesitic breccia with included acid fragments. 
The light colored streaks and spots in the fragments are "zones of 
growth" from which small specks of iron ore have evidently derived 

a portion or all of their material 62 

B, Photomicrograph of an- amygdaloidal fragment contained in the 

andesitic breccia; 105 diameters; ordinary light 62 

XII. A, Hand specimen of the amygdaloidal andesite. The amygdules 

may be plainly seen with a honey-combed mode of weathering 68 

B, Large rounded boulders of gabbro where a gabbro dike crosses the 
Fairmount-Denton road one mile northwest of Healing Springs, David- 
son County, N. C 68 

XIII. A, Photomicrograph of diabase, Davidson County, N. C; 30 diam- 
eters; ordinary light. Augite, olivine, plagioclase and magnetite. 

Ophitic texture 72 

B, Photomicrograph of diabase, Davidson County, N. C; 30 diam- 
eters; polarized light. Augite, olivine, plagioclase and magnetite. 

Ophitic texture 72 

XIV. Diagrams showing relations of joints, veins, dikes and schistosity. 
Ordinates equal abundance (number of observations) Obscissae equals 

trend 86 

XV. Diagram showing relations between compressive force, schistosity 

and directions of maximum jointing 88 

XVI. Longitudinal section of North and Inclined shafts of Silver Hill Mine . . 98 
XVII. Cross-section of North, Saw-mill and Inclined shafts, Silver Hill Mine, 

Davidson County, N. C 100 

XVIII. Plan of Silver Hill Mine, Davidson County, N. C 102 

XIX. Underground workings of Silver Valley Mine 106 

XX. Underground workings of Emmons Mine, Davidson County, N. G 116 

XXL A, Shaft houses at Emmons Mine 118 

B, Mill and smelter at Emmons Mine 118 

XXII. A, The "stringer lead" type of vein, showing stringers and seams of 
quartz and ore in a schistose country rock. This is a photograph of 
a polished section of the vein in the Gold Hill Mine. The Emmons 

vein is very similar 122 

B, Photomicrograph of Silver Hill ore; 40 diameters; section polished 
and etched by cone. HN0 3 . Scratched areas are chalcopyrite. 
Clouded areas are galena (deeply etched). Long shreds are an amphi- 
bole, probably actinolite. Section also contains a little sphalerite.. . . 122 

figures. PAGE 

1. Index map showing location of the Cid Mining District, Davidson 
County, N. C. (black portion) and the Carolina Slate Belt (shaded 
area) ^ 

2. Sketch of small glass sherds within a fragment of the volcanic breccia 
magnified about 88 diameters 50 

3. Sketch showing the amygdules within an andesitic fragment contained 

in the andesitic breccia. Magnified about 88 times 62 

4. Map of Conrad Hill ' ' 110 

5. Underground workings, Peters Mine. . . , 114 



INTRODUCTION. 



The following report is a geologic and economic investigation of 
the Cid Mining District of Davidson County, North Carolina, an 
area covering about 125 square miles. It also gives a detailed study 
of the occurrence and origin of the copper, silver and gold deposits 
included within the district, and description of all the mines that 
have been operated. 

This investigation shows that the "veins" or ore deposits may be 
grouped into four classes: (1) impregnations of ore in the schists; 
(2) stringer leads, ranging from intricating stringers and lenses of 
quartz to well-defined quartz veins, and agreeing in trend with the 
schistosity or cutting that structure at small angles; (3) cross veins, 
or well-defined quartz veins, which cut the schistosity at large angles 
and are usually barren ; and (4) replacement deposits, or zones carry- 
ing seams and lenses of ore, chiefly argentiferous and auriferous 
galena and sphalerite, in an extremely metamorphosed or highly 
silicified country rock. 

Chapter I gives a geographical and historical sketch of the district. 
Chapters II and III discuss the general geology of the district and 
give a detailed description of the rocks. Chapters IV and V relate 
to the physiography of the district and discuss very thoroughly the 
problems relating to structure and metamorphism. Chapter VI is a 
detailed description of the mines and prospects in the district, fol- 
lowed by a discussion regarding the genesis of these ore deposits. 
The results obtained in the investigation are summarized in Chap- 
ter VII. 

There is an appendix to the report which gives a bibliography of 
the Cid Mining District. 

This report has been prepared by Dr. Joseph E. Pogue, Jr., who 
did the field work in 1008 and conducted the laboratory investiga- 
tions in the Petrographical Laboratory of Yale University. The 
traverse map, which has been used as the base of the geological map, 
was made by Mr. R. L. Harrison, of the U. S. Geological Survey. 

The author and State Geologist wish to acknowledge their indebt- 
edness : To Mr. O. L. Stoner, of Linwood ; to Messrs. J. A. Shirley, 



14 INTRODUCTION. 

J. A. Prim and J. F. Peters, of Silver Hill, and to Messrs. O. O. 
Robinson, A. J. Beck, W. Cockreham and Alex. Hedrick, of Cid, for 
information and courtesies extended during the course of the field 
work ; to Dr. F. B. Laney, for looking over the field work, for numer- 
ous suggestions, and particularly for his previous work in the Pied- 
mont Plateau ; to Mr. D. B. Sterrett, for taking some photographs of 
rock specimens for the author; to Prof. Joseph Barrell, for sugges- 
tions and for a critical discussion of the main ideas presented in the 
chapter on structure and metamorphism ; and especially to Prof. 
L. V. Pirsson for his kindly interest and help at every stage of the 
investigation. 

Joseph Hyde Pratt, 

State Geologist. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE 




THE CID MINING DISTRICT OF 
DAVIDSON COUNTY 

NORTH CAROLINA 

By Joseph E. Pooue, Jb. ^ 



CHAPTER I. 

GEOGKAPHY AKD HISTORY. 
GEOGRAPHICAL SKETCH OF CID MINING DISTRICT. 

Location. — The area described in this report is a part of Davidson 
County, North Carolina. It is situated in the central portion of the 
State, within the Piedmont Plateau, and near the western boundary 
of an area of volcano-sedimentary rocks known as the "Carolina 
slate belt," which crosses the State in a northeast and southwest direc- 




Fig. 1— Index Map showing the location of the Cid Mining District (in black) and the 
"Carolina Slate Belt" (shaded). 

tion. The tract is about 13 miles long and 9 miles wide, covers 
approximately 125 square miles, and extends northeast from the 
Yadkin Eiver, which forms its southwestern boundary, 1 mile beyond 
the village of Cid. (See Fig. 1.) On the southeast it includes the 



North Carolina State Library 
Raleigh 



16 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

villages of Jacksonhill and Denton ; on the northwest, Fairmont and 
Silver Hill. The area is reached on the Carolina Central Railroad, 
a small branch line connecting with the main line of the Southern 
Railroad at Thomasville, and extending from that point through Cid 
to Denton, a distance of 20 miles. Not more than a dozen miles 
distant are Gold Hill, Thomasville, Lexington, and Salisbury. 

Topography. — Though a part of the Piedmont Plateau, the area 
in places is quite rugged. The chief surface feature is Flat Swamp 
Ridge, a narrow ridge which rises about 200 feet above the neigh- 
boring valleys and extends for nearly 7 miles through the central 
portion of the district. This ridge consists of Flat Swamp, Grice, 
and Surratt "mountains," and forms the backbone of a region which 
slopes into gently rolling country on either side. To the north the area 
is a succession of narrow ridges and rounded eminences, the more 
important of which are Kemp and Three Hat mountains ; the latter 
extending beyond the area mapped. In the southern corner, the 
country rises considerably to a conical-shaped hill, known as Bald 
Mountain, which is not included in the region described. The gently 
rolling country, though not so striking as the ridges, is quantitatively 
more important, and presents the usual well-rounded hills and gentle 
slopes typical of maturely dissected regions. 

Drainage. — The area is drained by the Yadkin River, which flows 
directly across it and cuts a narrow passageway through Flat Swamp 
Ridge. Of secondary importance are Abbott's Creek, Flat Swamp 
Creek, Lick Creek, and Cabin Creek, which pursue almost parallel 
courses, until they enter the river at nearly right angles to it. The 
network of smaller watercourses in general fails to show the regular 
arrangement of the more important streams. 

Soil. — The soil for the greater part is lean and not first-class farm- 
ing land. Once covered by a heavy growth of timber, which has been 
thinned by man and the devastation of forest fires, it now carries on 
the rougher portions a scant and scraggy covering of second growth 
timber, while the gentler slopes are mostly cleared and in part under 
cultivation. The ridges are extremely rocky ; in certain places num- 
bers of huge rocks abound, which have been not inaptly compared to 
"cockade hats" on account of their narrow, elongated outline. 

Climate. — The climate is equable and agreeable for nearly the 
entire year. The mean annual temperature is about 58° Fahren- 
heit ; the average yearly precipitation is about 51 inches, and well 



MWB CAROLINA LIBRARY COMMISSION 
RALEIGH, N. C. 

GEOGRAPHY AND HISTORY. 17 

distributed throughout the year. The region is free from prolonged 
droughts in the summer, as well as from excessive rain and snow 
in the winter. 

Culture. — The country is sparsely populated, and for the greater 
part by those who trust in the output of small farms for their liveli- 
hood. There are no large landowners, yet most of the inhabitants 
are independent and some sub-let a portion of their farms to tenants. 
Though too little attention has heretofore been directed toward bet- 
tering the schools, churches, and roads, the people are hospitable, 
favorable to outside interests calculated to develop their resources, 
and are paying more and more attention to features which make for 
social and economic improvement. The mining industry, formerly 
of importance, does not at present (1908) add to the activity of 
the region. 

PREVIOUS GEOLOGIC WORK. 
No detailed geological work has been previously done within the 
area embraced in the present report. The mines, however, from 
time to time received the attention of certain geologists and mining 
engineers, and mineralogists were interested in various finds of 
rare minerals. Other portions of the Carolina slate belt, on the 
other hand, have been the field of much investigation, and such views 
and results of the workers therein as have a general application to 
the area in hand will be here developed. 

In 1799 there appeared in the Medical Repository a letter by 
James Hall, 1 descriptive of a supposed artificial wall about 14 miles 
from Salisbury near the Yadkin Eiver; with a reply by James 
Woodhouse to the effect that the wall was composed of basalt. This 
was followed by no less than seven articles or letters, in addition to 
various notices, in which the wall was attributed twice 2 ' 3 to ante- 
diluvian man and five times 4 ' 5 ' 6 > 7 - 8 to igneous agency. These ar- 

in N?rth'£ll ^nTiT 1 * ? f t SUpp ?" ed A rtifici ^ ^11 discovered under the surface of the earth 
v 2 °1 799) i- 272-278 "* Woodhouse (and Doctor Woodhouse 's reply). Med. Repos., 

v. 5T180S; 397-40? 3h " Lett6rS ° n subterranean wal1 on the Yadkin in North Carolina. Med. Repos., 

Am. 3 Jour W sS:,i ? e h r n i, vSTS lV** ^"^ WaUS ^ S ° lid dikeS in the St&te ° f N ° rth CaroIina - 
227-234 WiS ' Zachariah - Remarks on a subterranean wall in North Carolina. Med. Repos., v. 4 (1801): 

w a ll 5 dSm h P °rpH e in J T^v, £ em , arks on a Ifttf of the R ev- Zachariah Lewis relating to a subterranean 

sw Ti JNorth Carolina. Med. Repos., v. 5 (1802): 21-24. 

North rSil^' James- Additional observations on the subterranean minerals near the Yadkin in 
JNortn Carolina. Mod. Repos., v. 7 (1804): 26-27. 

Repots Kuftv 148- d 51 CriPti ° n ° f ^ region in North Carolin a where gold has been found. Med. 
8 Cooper, Thomas. Floetz trap in North Carolina. Am. Jour. Sci., Ser. I, v. 4 (1822): 241. 



18 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

tides are of interest because they represent the earliest accounts of 
geological phenomena in central North Carolina. 
' In 1825 the first geological exploration of the country, including 
and adjoining the Cid District, was undertaken. In that year Olm- 
sted, 1 recently appointed State Geologist of North Carolina, called 
attention to the "great Slate Formation" which "passes quite across 
the State from northeast to southwest, covering more or less of the 
counties of Person, Orange, Chatham, Randolph, Montgomery, Ca- 
barrus, Anson, and Mecklenburg." He describes this formation, 
which is about 20 miles wide, as consisting principally of parallel 
ranges of Clay Slate or Argillite, occurring in perpendicular slabs 
of various complexions; together with numerous beds of petrosili-. 
ceous porphyry, soapstone, serpentine, greenstone, and whetstone 
slate or novaculite. The different members are described in but little 
detail. While the "slates" are recognized as differing from ordinary 
slates, no explanation for this variation is given. Mention is also 
made of the occurrence of placer gold within the slate belt 

In 1828 Rothe 2 attempted a fanciful explanation of this alluvial 
gold. He attributes its widespread occurrence to a great inundation 
"perhaps occasioned by the breaking through the Blue Ridge of 
waters accumulated on the other side," and their re-accumulation 
above the Narrows of the Yadkin, with the resulting deposition of 
the gold previously removed from veins by the force of the waters. 
The following year Mitchell, 3 in a more important paper than the 
preceding, recognized that "no stratum, except derived from rock 
decomposition, covers the upper country," and that the rock itself is 
the source of the gold through weathering. He further calls atten- 
tion to a member of the slate formation not mentioned by Olmsted : 
namely, a "conglomerate or breccia * * * sometimes exhibiting a 
schistose structure and sometimes destitute of any tendency to such 
a structure," which occurs in alternate layers with the slate. He 
emphasizes, moreover, the great diversity in appearance of the va- 
rious phases of the argillite. In 1830 Eaton 4 added the term "tal- 
cose slate" to those already used in describing the members of the 
slate belt ; speaking of it as occurring in association with novaculite. 

'Olmsted, Denison. On the gold mines of North Carolina. Am Jour. Sci., Ser I, v. 9 (1825); 5-15. 
Reoort on the geology of North Carolina, conducted under the Board of Agriculture. Kaleign, J. 

Ga1e 2Rothe, n ChlrlesE. Remarks on the gold mines of North Carolina. Am. Jour. Sci., Ser. I, v. 13 

3\iitchell, Eliaha. On the geology of the gold region of North Carolina. Am. Jour. Sci., Ser. I, 

•Eaton, Amos. The gold of the Carolinas in talcose slate. Am. Jour. Sci., Ser. I, v. 18 (1830) : 50-52. 



GEOGRAPHY AND HISTOEY. 19 

Little work was done for the next ten years. In 1841 Hodge 1 
attributed the concentrically weathered Piedmont boulders to glacial 
action, and mentioned the passage downward of the gold ores of 
Davidson County into undecomposed sulphurets. In 1842 Mitchell 2 
added little to what was already known of the slate belt. He recog- 
nized, in addition to argillite, hornstone, flinty slate, and jasper, 
interstratifled beds, sometimes massive and sometimes exhibiting a 
"slaty structure,'' composed of water-worn, siliceous and other peb- 
bles, united by a cement of silica. He mentions the occurrence in 
Davidson County of patches of "those rocks, by which a passage is 
made from slate to granite, these * * " * often colored green 
by epidote." 

In 1854 Leeds 3 spoke of the rocks of the gold region as "trappean 
belts of country * * * and ranges of hornstone slate" seem- 
ingly forming parallel bands. The trappean rocks include green- 
stone, hornblendic granite, feldspathic granite, syenitic granite, and 
a siliceous sub-crystalline rock, closely allied in its external charac- 
ters to hornstone. 

Thus the matter rested, until Emmons 4 in 1856, in his "Geological 
Eeport of the Midland Counties of North Carolina," developed the 
following views, representing the results of the most important work 
thus far done. He considers the slate belt composed of : 

"Slates and siliceous rocks which have been called quartzites. 
* *_ The slates are variable in color and composition. They 
are mineralogically clay, chloritic, and talcose slates, taking silica 
into their composition at times, and even passing into fine grits or 
hornstones, but still variable in coarseness. In the order in which 
they lie, the talcose slates and quartzites are the inferior rocks, 
though quartzite occurs also in the condition of chert, flint or horn- 
stone, in all the series." 

That the slates are sediments is considered proved by the occur- 
rence of "numerous beds containing rounded pebbles." Moreover, 
the adjacent granite is mentioned as the source of the sediments. 
A "brecciated conglomerate" is described as a "most remarkable" 

iHoi?e, James T The boulders and deposit gold mines of North Carolina. Assoc. Am. Geol. and 

rt,r- £ ts ii °£. ls t' 2d and 3d mset - (1841): 34 > 35 > and Am - Jour - Sci - Ser - I. v - 41 (1841): 182. 183. 
'Mitchell, Ehsha. Elements of geology; with an outline of the geology of North Carolina. 1842. 
With, map. 

o 3 ^frS' S o? P o h . en F.n n Notes on the gold re g ions of North and South Carolina. Min. Mag., Ser. I, 
v. £ (lo54): 27—34; 257- 269. 

*Emmons. Ebenezer. Geological report of the midland counties of North Carolina. New York. 
Geo, P. Putnam. Raleigh, Henry D. Turner. 1856. 
See also 

Emmons, Ebenezer. American Geology. Albany, Sprague & Co. 1855. 



20 



THE CID MINING DISTRICT OP DAVIDSON COUNTY, 



member of the series. It is "composed in the main of fragments of 
other rocks mostly retaining an angular form, but frequently rounded 
and worn rocks are inclosed in the mass." 

The "quartzite" is described in great detail and a variety of 
rocks are evidently included under this term. It is denned as an 
"uncrystalline kind of quartz, resembling as closely as possible com- 
mon gun-flint." There are porphyritic and amygdaloidal phases; 
the latter not recognized as such, but described as "greenish, and full 
of cavities, and frequently epidotic." The several varieties are con- 
sidered to be most probably deposited from solution. 

In point of age, the slates are consigned to the "Taconic System'^— 
a term proposed by Emmons to embrace those sediments occurring 
beneath the Silurian and above the "primary series" of igneous 
rocks. In support of this correlation is cited the resemblance in posi- 
tion and lithological character to the rocks of the original Taconic 
System, and also the occurrence of certain nodular or concretionary 
forms, which are considered fossil sponges and to be "the oldest rep- 
resentatives of the animal kingdom on the globe." To these forms 
is given the generic name "Paleotrochis," meaning "old messenger," 
and two species are differentiated, called, respectively, Paleotrochis 
major and Paleotrochis minor. Subsequent work has shown these 
interesting forms to be spherulites. 1 

During the next 19 years work was limited to the publication of a 
few notes on the Silver Hill Mine, an occasional mineralogical notice, 
and quite a variety of discussions as to the merits of Paleotrochis, 
which was "proved conclusively" to be of both organic and inor- 
ganic origin. 

In 1875 Kerr 2 published his "Geology of North Carolina," includ- 
ing a geological map of the entire State. He describes the slate 
series in practically the same terms as did Emmons, but in less detail 
and with the exception that they are considered Huronian in age. 

"The gold deposits, which are contemporaneous with the slates 
themselves, are of far greater importance than the true gold veins. 
* * * The gold in these slate beds, like the slates themselves, is 
derived from the destruction of the older rocks, and has been de- 
posited simultaneously." 

In 1888 appeared Kerr and Hanna's "Ores of North Carolina." 3 

•Oilier. Joseph Silas. Origin of Paleotrochis. Flis. Mit. Sci. Soe. Jour, v IB (1899): 59-67. 
*Kerr, Washington Caruthers Beport of the Geological Survey of North Carolina. lbio. 
'Kerr. \Y. C, and Hanna, G. B. Oies of North Carolina: being chapter II of the second volume 
of the Geology of North Carolina. Raleigh, Edwards & Broughton. 1888. 



GEOGRAPHY AND HISTORY. 21 

This is entirely of an economic nature and does not contribute to the 
geology of the slate formation. The Conrad Hill and Silver Hill 
mines are described in some detail, with drawings of the underground 
workings; but no theories as to the genesis of the ores therein are 
offered. 

In 1894 Williams, 1 in a brief but very important paper, recog- 
nized for the first time the occurrence within the slate belt of ancient 
acid volcanic rocks. He considers that these in the main are altered 
rhyolites. A sketch map of a portion of Orange and Chatham coun- 
ties is included, showing locations of volcanic rocks. Of a small area 
near Chapel Hill, the following description is given: "Here are to 
be seen admirable exposures of volcanic flows and breccias with finer 
tuff deposits which have been sheared into slates by dynamic agency." 
Suggestion is made that the "chert" or "hornstone" of Emmons may 
be of volcanic origin. 

The following year, in 1895, Becker 2 in his "Gold Fields of the 
Southern Appalachians" described the Carolina Slate Belt, referring 
it to the Algonkian. He recognizes the volcanic nature of portions 
of the slate series, speaking of the "porphyries" in the follow- 
ing terms: 

"They show flow structures in some cases and were probably in 
part glassy and tuffaceous rocks, yet they were most likely deeply 
buried at the time of the formation of the deposits." 

The cherts, quartz rocks, hornstones, etc., of former writers are 
thus described: 

"Under the microscope they show small inter-locking grains of 
quartz looking very much like vein quartz and giving no evidence 
of growth from fragments, but always mingled with minute scales 
of muscovite. There seems strong reason to suppose these masses 
due to decomposition and recrystallization of the acid volcanics." 

The greater portion of the gold within the slate is considered 
to have been deposited at the close of the great volcanic era, or dur- 
ing the Algonkian. Dikes are cited which seem connected with 
the deposition of the ore; and among others one occurring at the 
Silver Hill Mine is described thus : 

"A dike rock which seems to be a decomposed diabase lay in con- 

f K m }l la j! na ' Geor se Huntington. The distribution of ancient volcanic rocks along the eastern border 
of North America. (With map.) Jour. Geol., v. 2 (1894): 1-31. Also Ancient volcanic rocks along the 
eastern border of North America. Am. Geol., v. 13 (1894): 212 213 

i«*w ecke k Geor g. e F e ^i^ nd - Gold fields of th e Southern Appalachians. (In U. S. Geol. Survey, 
loin Ann. itep., pt. o, 1895.) 



22 THE CID MINING DISTRICT OE DAVIDSON COUNTY. 

tact with the ore, as appeared from masses on the dump." These 
are distinct from later intrusions of Triassic "olivine basalt" A 
theoretical discussion of the fissures is given. 

«j£ * * * the general tendency in the Southern Appalachians is 
to overthrust movements, it was a temporary reversal of this 
tendency which opened the fissure system of this region." 

The mode of filling the fissures by means of uprising solutions is 
considered, and brief descriptions of the Silver Hill, Silver Valley, 
and Emmons mines are included. 

The same year, 1895, Nitze and Wilkins 1 presented a paper in 
which they maintained that the gold ores of the slate formation are 
due to the "ascension of heated carbonated and alkaline waters, carry- 
ing silica, metallic elements, and sulphides in solution" and deposi- 
tion in open spaces, by relief of pressure, lowering of temperature, 
and perhaps chemical reactions. 

In 189G appeared the "Gold deposits of North Carolina" by Nitze 
and ITanna. 2 These authors identify within the slate series argil- 
laceous, sericitic, and chloritic schists. They distinguish between 
slates and schists in the following terms : 

a A great number of rocks have a true slaty cleavage, while others 
are more truly schistose ; i. e., the laminae are not essentially parallel. 
These structural effects are due to the action of dynamic metamor- 
phism on materials of different composition. The argillaceous type 
might more properly be called the slates * * * as they contain more 
uncrystalline matter, and possess a more definite slaty structure." 

In regard to the origin of these schistose and slaty rocks, they 
say: 

« * * * j n p ar t ? it seems they must be sedimentaries altered by 
dynamo- and hydro-met amor phism. * * * It does not seem prob- 
able * * * that these slates have been derived from the granitic 
and other more basic igneous masses lying to the west, for * * * 
these are supposed to be later intrusive bosses." 

The occurrence of volcanic rocks is recognized and noted. The 
dense siliceous rocks (hornstones, etc., of previous writers) are con- 
sidered to be most probably devitrified rhyolites. It is suggested that 
"there was more than one volcanic outbreak, and during at least one 
period of inactivity slates were deposited." Accompanying the acid 

iNitze, H .B. C, and Wilkins, H. A. J. The present condition of gold-mining in the Southern Appa- 
lachian States. Am. Inst. Min. Eng., Trans., v. 25 (1895): 661-796. 

2 Nitze, H. B. C, and Hanna, G. B. Gold deposits of North Carolina. N. C. Geol. Survey, 
Bull. 3, 1896. 



GEOGRAPHY AND HISTORY. 23 

volcanics are described "pyroclastic breccias and basic eruptives, 
which are usually schistose." These are described as follows : 

« # * # usually of a dark green color, and perhaps pyroxenic in 
composition, sometimes prophyllitic ; they cover large areas, and are 
often massive or only partly schistose ; again they are largely sheared 
into schists." 

The authors de-scribe a series of sedimentary rocks occurring in 
Union County in the southeast portion of the Carolina slate belt, 
which they consider of later age than the slates to the west and north. 
This new member in the slate series, which is termed the "Monroe 
Slates," forms "a considerable area of truly bedded and but little 
indurated or metamorphosed slates." 

In regard to the genesis of the ores, the following is in the main 
the view advanced. A force from the northwest developed normal 
faulting (this later than the "shearing" force), accompanied by the 
production of "spaces of discission," which were afterwards filled by 
uprising ore-bearing solutions. The origin of these deep-seated 
waters is connected with the "last stages of the volcanic activity 
that was general * * * ." The silicification of the slates and 
schists are likewise attributed to the ore-bearing waters. The ore 
deposits are Pre-Jurassic. Descriptions are included of the Conrad 
Hill, Silver Hill, Emmons, and Cid mines. 

Other articles by Nitze the same year 1 ' 2 and the following year 3 
do not add essentially to the views set forth above. The same may 
be said of Bulletin 10 of the North Carolina Survey by Nitze and 
Wilkins. 4 

In 1906 Weed and Watson 5 in a joint paper on the Virgilin a cop- 
per deposits considered a portion of the slate belt in the vicinity of 
Virgilina, Virginia. From a study of the schistose rocks occurring 
in this district, they drew the following conclusions: 

"1. The rocks have been greatly altered from pressure and chemi- 
cal metamorphism, as indicated in the prevailing schistose structure 
and the large development of secondary minerals. * * * 2. 
From structural, petrographical, and chemical evidence it is shown 
that the rocks are derived from an original andesite. * * * 

Nitze, H. B. C. Gold mining in the southern states. Engineering, v. 10 (1895): 821-844. 

"Nitze, H. B. C. Some late views of the so-called Taconic and Huronian rocks of North Carolina 
Elis. Mit. Sci. Soc, Jour., v. 13 (1896): 53-72. 

3 Nitze, H. B. C. The genesis of the gold ores in the central slate belt of the Carolinas. Eng. and 
Mg. Jour., v. 63 (1897): 628-629. 

4 Nitze, H. B. C, and Wilkins, H. A. J. Gold mining in North Carolina and adjacent South Appala- 
chian regions. N. C. Geol. Sur., Bull. 10, 1897. 

Weed, Walter H., and Watson, T. L. The Virginia copper deposits. Ec. Geol., v. 1 (1906): 309-330. 



24 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

3. The rocks are Pre-Cambrian in age and represent an area of 
ancient volcanic rocks * * * 

The same views, but in less detail, were put forward in earlier 
papers by each of the above authors. 1 ' 2 

In the same year appeared "A Keconnaissance of some Gold and 
Tin Deposits of the Southern Appalachians" by L. C. Graton. 3 
This is economic in nature and deals with an area to the southwest 
of Davidson County, consequently no descriptions of the mines of 
the Cid District are included. The gold deposits are divided into 
two types — fissure veins and replacement deposits — with transitional 
members. In regard to the genesis of the ores, the following are 
the summarized views advanced: 

"Concentrated solutions containing gold, silica, potash, sulphides, 
and oxides of iron and titanium ascended from great depths at high 
pressure and temperature. In the denser rocks they forced their 
way along crevices, forming veins. * * * 'In the more porous 
rocks the solutions permeated large masses and replaced the original 
rocks fragments. * * * The source of the ore material was at 
great depth below the surface. * ' '* * It seems certain that the 
vein solutions are genetically connected with * * granite 

intrusions. **."'* The deposition * * * was probably 
due partly to decrease of temperature and pressure * * * but 
was doubtless caused mainly by a disturbance of the nice equilibrium 
of solubility and concentration by the accession of substances dis- 
solved from the wall rock." 

In April 1908 Eaton 4 published an article on a flint-like slate 
from near Chapel Hill. A microscopic description is given, ac- 
companied by a partial chemical analysis, and it is concluded "that 
the rock has remained essentially unchanged since its consolidation, 
and that its formation was similar to that of an arkose, viz : that its 
component minerals are the detrital fragments of a rock or rocks rich 
in quartz and feldspar." This rock is probably the same as the 
"dense siliceous rocks," "cherts," and "hornstones" of previous 
writers, and most likely represents a silicified acid tuff. 

•Weed, Walter Harvey. Types of copper deposits in the Southern United States. Am. Inst. Min. 
Eng., Trans., v. 30 (1900): 449-504. 

2 Watson, Thomas Leonard. Copper-bearing rocks of Virgilina copper district, Virginia and North 
Carolina. Geol. Soc. Am., Bull., v. 13 (1902): 353-376. 

3 Graton, Louis Caryl. Reconnaissance of some gold and tin deposits of the southern Appala- 
rhi.ms. U. S. Geol. Sur., Bull. 293 (1906). 

4 Eaton, Harry Nelson. Micro-structure and probable origin of flint-like slate near Chapel Hill, 
N. C. Elis. Mit.'Sci. Soc, Jour., v. 24 (1908): 1-8. 



GEOGRAPHY AND HISTORY. 25 

The following month Laney, 1 in a thesis presented at Yale Uni- 
versity, on the Gold Hill Mining District, gave the results of a de- 
tailed study of a portion of the slate formation. His most impor- 
tant conclusion in regard to the slate series may be summarized in 
the following quotations: 

"The slates consist of heavy beds of bluish or grayish slates inter- 
bedded with which are rhyolite and andesite flows and heavy beds 
of dacitic tuffs. * * * The tuffs vary greatly, but are usually 
of medium texture. * • * * The coarser phases consist of sharply 
angular fragments of both rock and feldspar imbedded in a dense, 
fine-grained groundmass containing more or less clay * * * this 
rock grades into an exceedingly fine-grained rock felsitic in character 
and so dense that the microscope does not resolve it. This material 
has the chemical composition of a rhyolite or a silicified dacite, and 
is regarded as a fine volcanic ash. * * * The slates differ from 
the fine, dense tuffs only in the amount of the land waste. By a 
decrease in the amount of ash and at the same time an increase in 
the clay, mud, etc., the fine, dense tuff passes gradually into the 
typical bluish slate. * * * The series as a whole consists of 
alternating layers or bands of these types of rocks, the bluish slate 
largely predominating. The rocks as a rule are fairly massive and 
reasonably fresh, only locally presenting sheared and schistose facies. 
They all, however, show much silicification and the rhyolite is com- 
pletely devitrified." 

The slate series is considered separated from the igneous rocks 
to the west by a profound fault. The report includes chapters on the 
physiography and structure of the region; and the ore deposits are 
treated in great detail, including a microscopic study of the ores by 
reflected light. 

In September, 1908, the North Carolina Geological and Economic 
Survey published a geological map of the North Carolina extension 
of the Virgilina copper district prepared by Laney and Pogue. 2 
This is on the scale 1:24000. 



iLaney, Francis Baker. The Gold Hill Mining District of North Carolina. A thesis. Yale 
University, 1908; and published as Bull. 21 N. C. Geol. Survey. 1910. 

2 Laney, F. B., and Pogue, J. E., Jr. An outcrop map of the Virgilina copper district. Scale 1- 
24000. N. C. Geol. and Economic Survey. 1908. 



CHAPTER II. 

GENERAL GEOLOGY OR EIELD DESCRIPTION OE THE 

ROCKS. 

BJTKODUCTION. 

The portion of the Piedmont Plateau described in this report ex- 
poses the beveled folds of a great volcano-sedimentary formation. 
A traverse across the district from northwest to southeast passes 
over the eroded edges of once horizontal beds, which appear upon 
the surface as elongated belts and lenses. Their character indicates 
an origin during a period of great volcanic activity, without parallel 
except in past geologic ages. 

Wide bands of a sedimentary, slate-like rock, composed of vary- 
ing admixtures of volcanic ash and land waste, have the greatest 
areal extent. Intercalated with these occur strips and lenses of acid 
and basic volcanic rocks, represented by fine- and coarse-grained 
volcanic ejecta and old lava flows. The acid rocks include fine 
tuffs, coarse tuffs, and breccias, chiefly of a rhyolitic and dacitic 
character; together with flows of rhyolite and dacite. The basic 
series embraces fine tuffs, coarse tuffs, breccias, and flows of an an- 
desitic and trachy-andesitic stamp. Gabbro and diabase dikes cut 
the other formations. (See geological map, Plate IY.) 

The region has suffered a period of severe dynamic metamorphism 
or mashing, consequent upon a great compressive force which 
squeezed the beds into enormous folds; followed by a time of 
chemical alteration and mineralization; which in turn was suc- 
ceeded by a long period of erosion and weathering. The rocks have 
suffered to a variable degree from all these factors. In general, each 
formation has a massive and a mashed or schistose phase, with every 
gradation between the two. The passage of heated solutions has 
affected all formations, as evidenced by the mineralized zones, the 
abundance of quartz veins, and the high degree of silicification in 
many belts of rock, and the universal occurrence of infiltrated iron 
ores. Finally, erosion has planed off all the upper portion of the 
folded series; but weathering has proceeded in excess of erosion 
to such an extent that the region is now deeply decayed, so that only 



GENERAL GEOEOGY OR EIEED DESCRIPTION OF ROCKS. 27 

here and there do the rocks project through a thick mantle of decom- 
posed rock or soil. 

In spite of the changes undergone, the rocks occur in a number of 
well-defined, though related and transitional, types, which can be 
delineated with a fair degree of accuracy on the geologic map. These 
types will be briefly described, with attention only to those features 
which may be seen in the field. 

SLATE. 

The rock included under the term slate forms the greater portion 
of the area. It occurs in broad bands, with a northeast-southwest 
trend, separated from each other by belts of volcanic rocks. It shows 
upon the surface as low, elongated, parallel reefs or ledges, repre- 
senting in most cases the upturned edges of beds. These are never 
very abundant nor continuous, because the rock easily weathers to 
a soil. The outcrops trend in a northeast direction, commonly vary- 
ing from 40° to 50° northeast; usually dip steeply to the northwest; 
and they are often badly jointed. Their surface is ordinarily of a 
grayish, yellowish, or reddish color, due to weathering, and the rock 
is frequently ready to crumble into a mass of chips and fragments. 
The slate country is one of subdued relief; in it are never found nar- 
row ridges or steep slopes. 

Much of the slate is massive ; but in many portions of the district it 
has been mashed to a greater or less extent, so that it splits easily 
along certain directions. In its fresh and massive condition, it is a 
fine-grained, blue, green, gray, or black rock, at times showing well- 
defined bedding, bespeaking its sedimentary origin. Some of the 
mashed phases also show bedding planes; these only in part agree in 
direction with the schistosity. 

Broad bands of the slate make up most of the level country" on 
either side of Flat Swamp Mountain. The outcrops may be seen to 
best advantage along the roads and streams. Perhaps the best de- 
veloped and freshest outcrops of the slate occur in the bed of Buddie 
Branch (Plate VI, A), where the bedding and shistosity coincide in 
having a vertical dip. To the east of Cid the slate is also well de- 
veloped ; here it is greenish, only fairly massive, and bedding planes 
cut the schistosity at an angle. This is true of the entire north- 
east edge of the same strip, which extends past Denton and Jackson 
Hill to the Yadkin. As the river is approached, the formation be- 



28 THE CID MINING DISTKICT OF DAVIDSON COUNTY. 

comes lighter in color, and a multitude of narrow intercalations of 
tuffaceous rocks, often represented by single outcrops, are found. 
The slate area between Fairmont and Flat Swamp Kidge is much 
more uniform in character. It is massive near the ridge, but be- 
comes schistose as Fairmont is approached, and its outcrops are con- 
sequently more badly weathered. 

The passage from the slate into adjoining formations is usually not 
clear cut, but transitional in character. It appears that the slate is 
intimately related to the tuffs, with which it is associated. Indeed 
the slate is considered but a fine-grained tuff, with which is mingled 
a varying amount of the product of land erosion, so that through de- 
crease in amount of land waste, it actually passes into the fine tuff. 
The transitional character of the slate may be seen as any of the 
tuff lenses are approached. 

ACID FINE TUFF. 

The acid fine tuff occurs interbedded with the slate and the acid 
coarse tuff, and is transitional into each. It has no widespread areal 
extent, but is abundantly distributed in very narrow lenses, often 
represented by single outcrops. These are frequently intimately as- 
sociated with outcrops of the coarse tuff, and the two form tuff bands 
parallel to the belts of slate. Outcrops may also be found in many 
portions of the slate country, which are quite similar in size and 
shape to those of the slate, but differ in being much lighter in color. 

The rock varies considerably in appearance from place to place, 
depending upon its degree of silicification and schistosity. Much 
of the massive tuff is highly siliceous, varies in color from cream, 
through gray, to black, and breaks with a conchoidal fracture into 
chips with keen translucent edges. The outcrops are badly jointed 
and emit a metallic sound when struck with steel. This type re- 
sembles flint or chert, and is called locally "gun-flint." Another 
phase of the rock is less dense and not so siliceous ; it is usually light 
gray in color, and appears very finely granular. Still another phase 
is dark green in color, and resembles an arenaceous variation of the 
slate. Much of the fine tuff has undergone a variable degree of 
mashing, so that all gradations are found from the light colored, 
finely granular, massive rock into a sericite schist. It is sometimes 
difficult to distinguish the mashed fine tuff from the mashed slate; 
the former, however, is usually lighter in color, and is apt to be 
more highly colored on weathered surface. 



GENERAL GEOLOGY OR FIELD DESCRIPTION OE ROCKS. 29 

The belt of rock running northward toward Conrad Hill and in- 
cluding the Peters and Silver Hill mines, is made np largely of 
sericite schists. These are light colored, extremely fissile rocks, 
breaking into thin sheets which feel smooth and soapy and are quite 
soft. Upon weathering they take on the most diverse and brilliant 
colors, especially near mineralized zones. Associated with these oc- 
cur a number of outcrops which have not been so badly mashed, 
but that they show their original nature ; these are represented by 
both the fine-grained and the coarse-grained acid tuffs. Since these 
rocks can form sericite schists through mashing and are actually 
found in many places grading very gradually into them, it seems 
evident that this entire belt is made up largely of alternations of the 
two tuffaceous rocks, which, on account of their nature and favorable 
position, were involved in extreme mashing. 

A lense of fine tuff of different appearance occurs about two miles 
east of Fairmont. The rock here is a fine-grained, greenish one; 
slightly schistose and resembling somewhat a sandstone. The out- 
crops are not abundant. This peculiar variation, which bears a cer- 
tain analogy both to the slate and to a feldspathic sandstone, is not 
found elsewhere in the area. 

The highly siliceous fine tuff, the so-called gun-flint, occurs in 
abundant outcrops along the road from Cid to Lexington, and in the 
neighborhood of Jerusalem Church in particular the roadbed is nearly 
covered with fragments of this rock. An extremely dense phase of 
the same rock is found on the dumps at Silver Hill and Silver Valley. 

In the slate area which passes between Flat Swamp Mountain and 
Jacksonhill, many outcrops of the fine tuff may be found in associa- 
tion with the slate. Here it is sometimes massive and sometimes 
schistose; and more rarely very dense and siliceous. In the belt 
of coarse acid tuff along the northwest edge of Flat Swamp Ridge 
are many intercalations of the fine tuff. 

ACID COARSE TUFF. 

The acid coarse tuff occurs in northeast trending belts, which are 
separated from each other by bands of slate country. The outcrops 
are intimately associated with those of the fine tuff, so that the two 
are mapped together as acid tuff. It is also somewhat extensively 
distributed as narrow intercalations and lenses within the slate belts. 

As with so many of the other rocks of the district, the coarse tuff 



30 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

occurs in all gradations from a massive to a highly schistose condi- 
tion. Most of the outcrops reveal their fragmental nature upon fresh 
fracture, but with increasing difficulty in proportion as the rock be- 
comes more severely mashed, so that in some of the sericite schists 
formed from the coarse tuff, this feature becomes obscured. The 
outcrops are abundant and prominent; well rounded when massive, 
and narrow and elongated when schistose. The weathered surface is 
characteristically bumpy, due to the superior resistance of the frag- 
ments, and has a yellowish or grayish color, often the same as that of 
the lichens which cover it. On fresh fracture, the rock is -seen to be 
composed of a dense, dark colored groundmass, containing broken 
crystals of feldspar and a variable number of small, angular rock 
fragments. The fragments are usually one-half inch or less in 
diameter and represent several kinds of rocks. Most abundant are 
fragments of a dense, light colored, siliceous rock ; but pieces of slate, 
•sometimes showing bedding planes, and of a dark colored, basic rock 
are not uncommon. . (Plate II, A.) 

The coarse tuff is prominently developed along the northwestern 
side of Flat Swamp Eidge. It forms a band between the higher part 
of the ridge and Flat Swamp Creek, and constitutes a kind of ter- 
race intermediate in elevation. The outcrops vary from massive to 
somewhat schistose and- are extremely abundant — so much so that 
they interfere with the cultivation of the land. The belt contains 
many outcrops of the acid fine tuff, and sometimes a transition from 
this into the coarse tuff may be seen in a single outcrop. The slightly 
mashed outcrops are elongated at right angles to their schistosity and 
parallel to the direction of the belt as a whole. 

Just east of Kemp Mountain the acid coarse tuff occurs in a badly 
mashed condition; but still gives abundant proof on fresh fracture 
and weathered surface of its fragmental nature. The rock here con- 
tains a goodly number of dark colored, basic fragments, but not in 
excess of the lighter, siliceous fragments, so that it may still be 
considered an acid tuff. The outcrops are extremely narrow and 
stand up prominently and abundantly. Many are 20 feet long, 10 
feet high, and 5 feet thick at the base. (Plate II, B.) These are 
very striking in appearance, occurring, as it were, in troops. Similar 
outcrops have been very appropriately compared to military or "cock- 
ade hats." 

The belt of sericite schists and mashed tuffs, which extends past 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE II. 



hM;!?'^ 






#,S- ^ 



— i. rvj 



••>':.; 



A. Outcrop of coarse acid tuff, showing its rough weathered surface, from 

NEAR FLAT SWAMP RIDGE, DAVIDSON COUNTY, N. C 




Narrow and elongated outcrops of the mashed acid coarse tuff, east of kemp 
mountain, davidson county, n. c. similar outcrops have been 
described as resembling "cockcade hats." 



GENERAL GEOLOGY OR FIELD DESCRIPTION OF ROCKS. 31 

Silver Hill, has already been discussed. This is regarded as the 
final result of the mashing of intercalations of the fine and coarse 
acid tuffs. 

The location of a number of other occurrences of the coarse tuff 
may be seen by reference to the geologic map. Those mentioned, 
however, are sufficient to indicate its most typical development. The 
nature of the rock is such that it could have been formed in no other 
way than as the result of explosive volcanic activity. 

ACID YOLCA1YIC BRECCIA. 

The acid volcanic breccia is practically confined to one band, 
mostly about a half mile in width, which includes Flat Swamp Kidge. 
and extends in a northern ly direction to Cid. Associated with the 
breccia are found outcrops of the acid tuffs, flows of rhyolite and 
andesite, and long strips of andesitic tuffs and breccias. (Plate 
III, A.) 

The volcanic breccia is twofold in character, and comprises both 
a brecciated phase of rhyolite and a very coarse acid tuff with frag- 
ments predominant over groundmass and larger in size than one- 
half inch. The rock is locally called "mountain rock" ; its outcrops 
are large in size and extremely abundant. Enormous boulders up 
to 20 and 30 feet in diameter are frequent, and, with larger, half 
buried masses, make up rocky ridges which are almost impassable. 
(Plate III, B.) Great concentrically weathered plates are at every 
stage of peeling off. Where most exposed the rock becomes white 
and pitted upon its surface. Further weathering forms a porous, 
sponge-like exterior which is characteristic. Where plates have re- 
cently peeled off the rock is fairly fresh, light greenish gray in color 
and spotted with numerous feldspar crystals and light colored, angu- 
lar rock fragments. In places the phenocrysts and fragments are so 
arranged as to strongly suggest flow lines. Most of the outcrops are 
very massive and somewhat jointed. In the vicinity of Cid some 
have undergone a minor degree of mashing. 

When freshly broken, the breccia has a mottled grayish color. A 
great number of light-colored, angular fragments make up most of 
the surface. Groundmass and broken phenocrysts fill in between 
the fragments. Irregular masses of black or dark-green material, 
present in some phases of the rock, are seen on close inspection to 
represent basic fragments. These are never very abundant. 



32 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

By a gradual decrease in number and size of fragments, the breccia 
passes imperceptibly into the rhyolite ; and in almost any part of 
the formation isolated outcrops of the rhyolite may occur surrounded 
by the breccia. Part of the breccia for this reason is considered a 
brecciated form of rhyolite; that is to say, the viscous rhyolitic 
magma hardened first upon its surface, and this was broken by the 
movement of the liquid mass beneath into angular fragments, 
which became incorporated in the molten paste. Erosion has planed 
across the mass, exposing part rhyolite and part rhyolitic breccia. 
All of the rock mapped as acid volcanic breccia, however, is not 
regarded as having such an origin. Much of the breccia is probably 
a very course tuff, or ordinary air breccia, with predominant frag- 
ments. It is not practical, nor indeed possible, to separate the two 

phases in the field. 

KHYOLITE. 

Rhyolite occurs in narrow bands, associated with the acid vol- 
canic breccia, into which it grades. Sharp lines between the two 
cannot be drawn. It is found best developed along the highest parts 
of Flat Swamp Ridge. 

The rhyolite forms prominent, rounded outcrops, similar to those 
of the volcanic breccia, but usually not as large. The rock is pre- 
dominantly massive and is somewhat jointed. Its surface is smooth 
and of a light gray or white color. In places contorted and wavy 
lines, indicative of flowage, are visible. ' The rock is brittle and 
breaks with a conchoidal fracture into pieces with keen translucent 
edges. Upon fresh fracture, it appears black, dark green, or grayish 
green; with feldspar phenocrysts uniformly, though not abundantly 
distributed. Some phases are exceedingly dense and can be distin- 
guished with difficulty from the highly silicified acid fine tuff. 

The rhyolite has its greatest areal extent in an elongated lense 
occurring on the crest of Flat Swamp Mountain. This represents 
the exposed portion of an ancient lava flow. Here the rock is mas- 
sive and surrounded by the volcanic breccia. The rhyolite very 
gradually passes into a rock containing a few siliceous fragments, 
and this in turn is transitional into the normal breccia with nu- 
merous fragments. Occasional outcrops of the rhyolite may be found 
wholly enclosed by the breccia. Two other narrow lenses of the 
rhyolite, forming subordinate ridges, occur a little to the north- 
west of the main ridge, between it and Flat Swamp Creek. Along 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE III. 




A. Outcrop of the acid volcanic breccia from flat swamp mountain, Davidson 



COUNTY, N. C 




B. Enormous outcrops of the acid volcanic breccia upon surratt mountain, Davidson 



COUNTT, N. C 



r 



i 



GENERAL GEOLOGY OR FIELD DESCRIPTION OF ROCKS. 60 

the entire length of Flat Swamp Mountain, from the river to Heal- 
ing Springs, isolated outcrops of the rhyolite are frequent. 

A number of outcrops may also be found upon Grice and Surratt 
Mountains, but are not extensively developed: the volcanic breccia 
always surrounds such occurrences. Further to the northwest, in 
the continuation of the same belt of breccia, after Flat Swamp Ridge 
has changed into a hilly country, the rhyolite is abundantly de- 
veloped. Its association with the breccia, however, is still so in- 
timate that in no cases are sufficient outcrops grouped to render it 
possible to map a small lense of this rock. East of Cid some of 
the rhyolite has undergone a slight amount of mashing. One 
occurrence shows a massive core of rhyolite passing on either side 
into a schist, which somewhat resembles some of the schistose slates. 
South of the Silver Valley Mine are many outcrops of the rhyolite, 
but even here the breccia is in predominance. 

DACITE. 

Dacite is confined to an area of oval outline represented by Kemp 
Mountain. Its outcrops resemble the outcrops of rhyolite, in that 
they are abundant, rounded, and light in color. The rock is less 
siliceous than the rhyolite, and in consequence is more difficult to 
break with a hammer. On fresh fracture it is grayish-green and 
phenocrysts of feldspar and small, dark green patches of chlorite 
and biotite are discernible. Some of the feldspars are slightly 
greenish. 

Kemp Mountain rises abruptly from Lick Creek which flows 
along its eastern border, and appears from this point of view to be 
a narrow ridge. Its slopes, however, are more gentle in all other 
directions. This occurence probably represents the remnant of an 
old lava flow, of slightly more basic nature than the flows of rhyolite. 
Its rounded contour on the map is due to the fact that the observer 
is not looking down upon the upturned edge of the flow, but more 
nearly upon its horizotal surface. Since there is no direct evi- 
dence of flow structure, it is possible that the mass may represent 
an old volcanic neck or conduit, or perhaps an intrusion which never 
reached the original surface. The first explanation is simpler, more 
in accord with structure, and is consequently preferable. 



34 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

ANDESITIC FINE TUFF. 

The andesitic fine tuff is a fine-grained phase of the andesitic 
coarse tuff and breccia, and represents consolidated dust and ashes 
from explosive- eruptions of more basic character than those which 
gave rise to the acid series of rocks. Fragments are almost entirely 
wanting and are never visible to the naked eye. Upon addition of 
these, the rock passes into the andesitic coarse tuff and breccia. 
In no place is its areal distribution of sufficient extent to show 
upon the geologic map. Its separate description is warranted from 
its analogy to the acid fine tuff. 

The rock is dense and somewhat less siliceous than its acid ana- 
logue. In color it is either greenish or green mottled with purple. 
Outcrops are small, somewhat rounded, of a grayish-green exterior, 
and rough to the touch. 

ANDESITIC COAKSE TUFF AND BRECCIA, 

The andesitic coarse tuff, composed of groundmass, phenocrysts, 
and a subordinate number of fragments, and the andesitic breccia, 
with predominant and larger fragments, are included under one 
head. Their intimate association makes it impossible to separate the 
frrco in the field. No evidence is found that part of the andesitic 
breccia is a flow breccia. 

The andesitic tuff and breccia forms long, narrow strips and 
broader lenses of important areal extent ; alternating with the areas 
of the slate and the acid series of volcanic rocks. It ranges all the 
way from a very massive variety, made up almost wholly of green 
fragments, to a greenstone schist, which in itself contains little evi- 
dence of its fragmental nature. The outcrops are abundant and 
prominent (Plate V, A) : when massive, they are low and well 
rounded; with increasing degree of schistosity, they become elon- 
gated and narrow, like inverted wedges, and resemble much in shape 
the "cockade hat" outcrops of the mashed acid coarse tuff. Only 
a few occurrences fail to have a bumpy weathered surface, which 
eals the fragmental nature of the rock even when this feature is 



rev 



not observed on fresh fracture. 

The massive rock is %heavy, tough, dark-green, and composed al- 
most entirely of green fragments up to % inch and larger in 
diameter. Dark green material, containing feldspar phenocrysts, 
fills the space between the fragments. Numerous particles of 



GENERAL GEOLOGY OR FIELD DESCRIPTION OE ROCKS. 35 

pyrrhotite are often present. More schistose varieties appear less 
f ragmental ; because fragments are converted into secondary minerals. 
Often the mashed rock is somewhat lighter in color than the mas- 
sive variety. 

Jnst west from Bald Mountain occnrs an area of rather massive 
coarse tuff and breccia. Outcrops are abundant, but not large, and 
contain considerable pyrrhotite. The soil is a brilliant red and 
sticky; its color is doubtless due to the oxidation of the pyrrhotite. 
The formation here seems little mineralized, except by iron ore. 
A lens^ of the same rock occurs southeast of Denton. Here it is 
not as massive. The rock is again seen, and in a massive condition, 
about a mile east of Kemp Mountain. 

A long narrow intercalation of the same rock is found along the 
northwest edge of Flat Swamp Eidge, separating the acid coarse tuff 
and the acid volcanic breccia. This extends from near the Yadkin 
River to within two miles of Cid; the outcrops have undergone 
a variable degree of mashing, and range from massive to fairly 
schistose. Beginning a half mile east of Snyder's Mill, a parallel 
band extends practically to Cid. Within this band are found speci- 
mens which contain large f ragmental inclusions of an acid rock. 
Immediately west of the Silver Valley Mine is found a small lens 
of the schistose basic breccia. 

The andesitic tuff and breccia has its greatest areal extent in a 
lens beginning northeast of the Silver Hill Mine and extending 
to Three Hat Mountain. (Plate V, A and B.) Here the rock 
varies considerably ; but all occurrences are more or less schistose. 
Outcrops are abundant and large, and mostly elongated. The re- 
sulting topography is rugged. (Plate V, B.) Flows of andesite 
are associated with the fragmental rock. 

Southwest of Silver Hill occurs a small area of the breccia, which 
has been mashed into resemblance to the slate in which it occurs. 
The difference is brought out on the weathered surface. A short 
distance to the east occurs a larger area intercalated with a lense 
of acid tuff. Numerous other smaller occurrences of the fragmental 
andesite are found throughout the district. 

The wide distribution of the type of rock described suggests the 
great complexity of the volcanic period, during which it was formed. 
There were undoubtedly many alterations between outbreaks of acid 
:and comparatively basic magmas. 



36 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

ANDESITE. 

Andesite is of very limited occurrence within the district. It 
forms several narrow strips and lenses of small areal extent, which 
represent the remnants of old flows. The rock is massive, somewhat 
jointed, and mostly porphyritic ; that is, it contains recognizable crys- 
tals of feldspar in a fine-grained matrix. In one place the rock is 
amygdaloidal, and is filled with small, round and oval areas of green- 
ish material, representing the vesicles of a surface lava subsequently 
filled with infiltrated material. The outcrops are not large, but are 
fairly abundant, and are usually rounded. 

The massive andesite is a fine-grained rock, varying in color from 
greenish-gray, through epidote green, to dark bluish-purple, in which 
small specks of epidote and crystals of feldspar may be usually recog- 
nized. The rock is tough and heavy. The amygdaloidal phase is 
unmistakable; for its distinctive texture and honeycombed appear- 
ance on weathered surface are features possessed by no other rock 
in the district. 

A strip of the andesite about 100 yards wide and over a mile long 
crosses the Fairmont-Denton road southeast of Grice Mountain. The 
rock is dark blue on fresh break ; its weathered surface is a dull gray 
and rough like coarse sandpaper. Upon either side, standing up in 
fairly prominent, well-rounded ridges, occurs the acid volcanic brec- 
cia. This occurrence of andesite represents the upturned edge of 
a flow. 

The amygdaloidal andesite is found on the southwest end of Three 
Hat Mountain. A mile and a half southwest of this occurrence, a 
dense phase of more alkalic nature forms a small eminence. This 
might more properly be called a trachy-andesite. A half mile east 
of Kemp Mountain also occurs a trachytic phase of the andesite. 
This phase in hand specimen resembles the dacite of Kemp Moun- 
tain. In position it is closely associated with a lense of massive 
andesitic breccia. Other occurrences within the district are of lim- 
ited extent. 

DIKE KOCKS. 

GABBKO. 

Gabbro occurs widely and abundantly distributed throughout the 
district in the form of dikes. It shows Upon the surface as rounded, 
yellowish boulders, locally called "nigger-heads," ranging in size up 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE V. 







A. Wedge-shaped outcrops of the mashed andesite breccia a mile west of 

THREE HAT MOUNTAIN, DAVIDSON COUNTY, N. C. 




B. Weathered surface of the andesitic breccia, showing the characteristic billowy 

OR BUMPY EXTERIOR. THREE HAT MOUNTAIN, DAVIDSON COUNTY, N. C. 



GENERAL GEOLOGY OR FIELD DESCRIPTION OF ROCKS. 37 

to 9 or 10 feet in diameter, and distributed in lines following the 
trend of the dikes. The largest dikes are usually more or less promi- 
nent topographic features in the shape of low, well-rounded ridges 
or mounds. (PL XII, B.) This, together with the abundance of 
boulders, renders their tracing a matter of little difficulty. From an 
eighth of a mile in width and three or four miles in length, the dikes 
range down in size to those which are exposed upon the surface by 
the presence of only a few boulders. The dikes are most abundantly 
developed in the vicinity of Fairmont, on either side of Flat Swamp 
Mountain, near Lick Creek Church, north of Denton, and a mile 
southwest of Silver Valley. A traverse from any point- across the 
district, along a line at right angles to the trend of the formations, 
would hardly fail to cross a number of gabbro dikes of various 
dimensions. 

The trend of the dikes in all cases coincides with the schistosity of 
the formations in which they occur. Moreover, the large majority 
of the dikes are found in the slate or acid tuff ; while the more mas- 
sive formations, such as acid and basic flows and breccias, are com- 
paratively free from them. The -schistosity is therefore considered 
to have been developed prior to the introduction of the dikes, and to 
have been, as an easy line of yielding, a controlling factor in their 
introduction. An apparent exception occurs about a mile southwest 
of Silver Valley mine, where a large dike, after following the schis- 
tosity for a mile and a half, branches to the left at an angle of 60°, 
and continues an equal distance in a northerly direction. In mak- 
ing this bend, it passes from a fairly schistose part of a formation 
into a rather massive phase. Jointing was probably in this case the 
dominant factor in controlling the introduction of the molten gabbro; 
yet the schistosity controlled as long as it was present. 

A particular dike will be found to vary in width from place to 
place, and in general will tend to pinch out at either end. The con- 
tacts between the dikes and adjacent formations are much obscured 
by weathering; so that it is impossible to discern any contact effects. 
The deeply weathered nature of the contacts, however, bespeaks a zone 
susceptible to alteration and doubtless rendered so by contact action. 
Jointing is well developed, and of such a nature as to indicate the 
operation of a force after the introduction of the dikes. 

The gabbro is a greenish-gray rock, of medium grain and homo- 
geneous texture, in which crystals of green hornblende and areas of 



38 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

opaque feldspar may be recognized. It is tough and heavy and 
very susceptible to weathering. In point of age, it is considered the 
second youngest rock in the district, since it cuts the other formations,, 
and is itself cut by dikes of diabase. 

1)1 A BASK. 

Diabase occurs widely, though not abundantly, scattered through- 
out the district in the form of dikes, which show upon the surface as 
narrow lines of rounded, yellowish boulders, locally called "nigger 
heads." These dikes prefer no particular formation, but are found 
universally distributed, cutting the other formations. They vary in 
size from a few feet in width and a few yards in length, to the largest, 
about a hundred feet in width and slightly over a mile in length. 
The majority conform to the former, rather than to the latter, dimen- 
sions. In trend they also vary, but the more common directions are 
included between N. 30° E. and N. 30° W. The trend of the dikes 
coincides with important joint directions. 

In two localities the diabase dikes are found cutting the gabbro : 
one about a half mile southeast of Fairmont ; and the other at a point 
one-half mile southeast of Flat Swamp Mountain and one-half mile 
-southwest of the Healing Springs- Jacksonhill road. The diabase is 
therefore younger than the gabbro, and its introduction seems at least 
in part conditioned by a set of joint planes, which are also younger 
than the gabbro, since they involve it. It is possible that original 
jointing may have controlled the introduction of many, or even all, 
of the dikes. 

The diabase is a massive, fine-grained, dark blue rock ; very tough 
and with a waxy luster on fresh fracture. Upon examination it is 
seen to be a closely knit aggregate of dark colored minerals, among 
which striated feldspar may be recognized with the hand lens. 
Although the rock is high in olivine, this constituent can not be recog- 
nized. The. diabase is doubtless of Triassic age, because a dike rock 
of similar character occurs in an adjoining Triassic belt about 50 
miles to the east, and in places is found cutting both the slates and 
sandstone. This conclusion is borne out by the unusual freshness of 
the diabase, which suggests a rock of post-Paleozoic age and one that 
has not suffered from dynamic metamorphism. 



CHAPTER III. 

A DETAILED DESCRIPTION OF THE ROCKS. 
INTKODUCTION. 

The area described in this report is composed of a number of rock 
types, distinctive in character, but intimately related in mode of 
origin. The surface bevels the upturned edges of once horizontal 
beds of slate, with their abundant intercalations of acid and basic 
tuffs, breccias, and flows. The region beyond doubt is indicative of 
ancient volcanic activity on a large scale. 

The slate is not a normal product of land erosion, but bears evi- 
dence of a peculiar origin by a liberal admixture of fine-grained vol- 
canic ejectamenta. With decreasing amounts of land waste, and 
increasing proportions of ash, this rock grades into a fine-grained 
tuff of acid nature. This, in turn, with increased size of material, 
passes into an acid coarse tuff, composed of ash, lapilli, broken crys- 
tals, and rock fragments. Closely related is an acid volcanic breccia, 
made up largely of angular rock fragments and grading into acid 
flow rocks. The latter are of two kinds, rhyolitic and dacitic, and 
represent ancient lava flows. Intimately associated with the slate 
and acid rocks, and alternating with them, occurs a series of basic 
fragmental rocks and flows. These are of an andesitic nature and 
comprise fine tuffs, coarse tuffs, breccias, and old lava flows of both 
porphyritic and amygdaloidal habits. 

This entire series, built up as a unit during a long period of time, 
has been folded, mashed, and altered. The degree of metamorphism 
has varied from place to place, so that each type of rock has a two- 
fold character ; comprising a badly altered or schistose phase, and a 
less badly altered or massive phase. A study of the badly altered 
types, in which the character of the original rock is masked by sub- 
sequent changes, will yield little as to their true nature. It is only 
by first considering the massive, relatively unchanged rocks, and 
afterwards proceeding to their more altered derivatives, that the orig- 
inal nature of each phase can be ascertained. This, then, is the 
mode of procedure adopted in the following descriptions. 

Each rock type will be classified according to the characters ex- 



40 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

hibited by its massive occurrences. Otherwise, quite diverse rocks, 
which had undergone the same degree of metamorphism, would fall 
together. (See geological map, PL IV.) 

SLATE. 

The sedimentary rock, composed of varying admixtures of land 
waste and volcanic ash, is comprised under the term slate. This 
rock has the most widespread occurrence of any type of rock within 
the district, It underlies, and has given rise to, the greater portion 
of the area of gentle slopes. It appears in small outcrops or reefs, 
standing on edge and mostly badly weathered, occurring at short 
intervals along the roads and streams. 

Macroscopic description. — A wide range of appearances is pre- 
sented by the slate. When fresh it is dark green, dark to light blue, 
or grayish-black to black. With increasing proportions of ash, these 
colors grade into lighter shades, and finally into light grays and 
whites. Upon weathering, the colors brighten and become quite 
diverse, and sometimes even brilliant. Shades of purple, blue, green, 
red, yellow, and gray in endless variations may appear. In texture 
the slate is dense, so that little can be discerned with the naked eye. 
In certain specimens small specks of biotite may be plainly recog- 
nized. In many occurrences bedding planes are visible (PI. VI, B) ; 
and often a certain degree of schistosity has been developed. Some- 
times the bedding and schistosity coincide ; more often they do not. 
There are phases of the slate which have been changed into sericite 
schists. These probably contain much tuffaceous material. 

Microscopic description. — The slate is so fine-grained that the 
microscope reveals only indifferently its mineralogical content. The 
highest power shows a dense, crypto-erystalline groundmass of a 
grayish to a greenish color, made up. of an aggregate of quartz and 
feldspar, difficultly distinguishable and knit together by numerous 
sericite fibers. Often material of a higher index of refraction is 
intermingled, which consists mostly of grains of epidote and clino- 
zoisite, with occasional small patches of chlorite. Variable but small 
amounts of kaolin and organic matter may be present, Often shreds 
and patches of a greenish, pleochroic biotite, of very ragged outline 
and porous, sponge-like interior, are uniformly distributed. Fre- 
quently associated with them are ragged, porous masses of black 
material, perhaps partly iron ore and partly organic matter. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE VI. 







A. Typical outcrop of slate in buddle branch, southeast of silver hill, 

DAVIDSON COUNTY, N. C 




: :%^ m 



9] 



10 



11 



113 



B. Hand specimen of a black slate with cross bedding strikingly 

BROUGHT OUT ON THE WEATHERED SURFACE. 



A DETAILED DESCRIPTION OF THE ROCKS. 



41 



Bedding and the arrangement of the secondary minerals are the 
chief textural features. The bedding visible in hand specimen is 
shown by the low power to be due to a uniform variation in size of 
grain along certain lines. In the great majority of cases this was 
undoubtedly caused by changed conditions of sedimentation whereby 
coarser or finer material was deposited. In some instances, espe- 
cially in those where the rock has had some degree of schistosity coin- 
ciding with the bedding planes imposed upon it, one must recognize 
that solutions, rising along certain lines, may have produced a re-crys- 
tallization and a consequent banding. In one outcrop of slate may 
be seen the interesting occurrence of cross-bedding, strikingly brought 
out on the weathered surface and easily visible under the microscope. 
The secondary minerals are due both to dynamic and chemical 
metamorphism. The biotites and sericite are the result chiefly of 
the former. The biotite has no particular arrangement; the seri- 
cite has a tendency to align itself at right angles to the force induc- 
ing schistosity. Both minerals increase in amount with the degree 
of mashing. 

CHEMICAL COMPOSITION. 

A determination of the alkalies in a typical black slate is given in 
the following table. Two analyses of slates from the Gold Hill 
region, and two of "slate" from the Haile Mine of South Carolina 
within the same belt of rock, are included for comparison. 

ANALYSES OF SLATE.* 





I 


II 


III ■ IV 


V 


Si0 2 




52.62 
33.20 
4.04 


62.46 i 61.02 
16.10 j 25.54 

1A7 \\ 4 04 
5.49 j 4 - U4 
2.27 1 0.14 
0.36 ' 0.60 
2.16 ! 2.19 
2.85 I 1.81 


44.61 


AI2O.3 




31.57 


Fe 2 3 -- 




3.55 


FeO — 




MgO 




0.27 
2.52 
3.80 
0.49 


0.22 


CaO 




0.20 


Na 2 . 


1.61 
2.07 


6.96 


K2O 

H2O— 


6.97 
5.80 


H 2 0+..__ 






co 2 _. 




0.66 




S 




0.26 












Total 




97.67 


96. 17 99. 96 


99.88 









For further comparison an average was made of the percentage 
of alkalies found in the 33 slates which were analyzed in the chemi- 



I. Partial analysis of Black Slate, Yi mile south of Silver Hill. A. S. Wheeler, Analyst. 

II. Analysis of typical Black Slate, Gold Hill, N. C R. T.Allen, Analyst. Laney: Gold Hill 
Mining District: 41. 

III. Analysis of typical Banded Blue Slate, Gold Hill, N. C A. S. Wheeler, Analyst, Ibid.: 41. 

IV. and V. Analysis of "Slate" from the Haile Mine, S. C. Chas. Baskerville, Analyst. Nitze & 
Hanna: Gold Deposits of North Carolina: 34. 



42 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

cal laboratory of the United States Geological Survey from 1880- 
to 1903. 1 These include normal slates from Vermont, New York, 
Pennsylvania, Michigan, Wisconsin, and Minnesota. The result is 
as follows : 

Average Na 2 0.89% 

Average K 2 3.68% 

The proportion of soda to potash is 1:4.1. In only two of the 
thirty-three slates was the percentage of soda greater than one-half 
the percentage of potash. These figures show that the normal slate, 
during an ordinary cycle of land erosion, loses soda much more 
readily than potash; so that the final result is a preponderance of 
potash over soda, irrespective of the original proportions. When 
the reverse is found to be the case, special conditions must be sought 
to explain this unnatural relation. 

In the slates of the Carolina Slate Belt, it is seen from the 
analyses given that the soda is about equal to, or in greater amount 
than, the potash. According to the quantitative nomenclature, the 
Carolina slate is sodipotassic to dosodic ; whereas a normal slate is 
dopotassic. This feature indicates that the rock has not undergone 
a normal cycle of erosion, for such would have brought it in line 
with the average slate. On the contrary, it suggests that the origi- 
nal material of the rock was transported only a short distance, and, 
further, that the material was presented to the transporting agent 
in a condition of mechanical disintegration. A long transport of 
finely comminuted material would have resulted in the deposition of 
sediments low in soda. A long period of chemical weathering, pre- 
vious to transportation, would have had the same effect. The con- 
clusion, which is strengthened by the geologic occurrence and rela- 
tion to the tuff deposits, is : that the slates were derived chiefly from 
great masses of volcanic ejecta, and deposited by water, with varying 
amounts of land waste, at no great distance from the source of the 
material. 

Classification. — It is realized that the type of rock just described 
does not, in all its phases, correspond to a true slate. 2 Yet the term 
slate is applied, and for two reasons : First, the rock is an admixture 
of land waste with variable amounts of tuffaceous material, which has 

iClarke, F. W. Analyses of Rocks. U. S. Geol. Survey, Bull. 228 (1904): 337, 338, 339, 340, 341, 342, 
344, 345, 346. 

2 " Slates are dense, homogeneous rocks * * * characterized by a remarkable cleavage, by 
means of which they split into broad, thin sheets * * * The slates represent * * * the finest 
material of land waste by erosion * * * With such material more or less volcanic dust and debris 
tuffs may be mingled." Pirsson, L. V. Rocks and Rock Minerals: 369. 



A DETAILED DESCRIPTION OF THE ROCKS. 43 

become indurated and had a certain degree of slaty cleavage imposed 
upon it. Second, many specimens so strongly resemble in appear- 
ance a normal slate that any other term would be misleading. 

WEATHERING. 

The weathered slates present a wide diversity in appearance, de- 
pending upon differences in composition and degree of metamorph- 
ism. There is a varying balance between the forces of mechanical 
and chemical disintegration. A massive, badly-jointed slate suffers 
much from the former; a severely mashed or schistose phase yields 
readily to the attacks of the latter. Slight variations in composition 
introduce further complications. The result, therefore, is that no 
two outcrops are exactly alike, and one is apt to consider the forma- 
tion more complex than it is, forgetting that the forces of weathering 
concentrate upon and accentuate original differences, however slight. 

Joint planes and cleavage cracks afford easy access to solutions. 
The first effect of weathering is a yellowish staining along these lines 
and upon the surface. This proceeds inward until the entire ex- 
posed portion of the outcrop becomes a shade of yellow. Often a 
block of slate will show a line of demarcation between the weathered 
exterior and the unweathered core. The greater the amount of 
schistosity, the more uniformly and rapidly does the weathering pro- 
ceed, with the development frequently of quite vivid colors. The 
rock finally crumbles into small chips and fragments of dull yellow 
tones. The resulting soil is filled with these chips, so that its nature 
is often apparent at a glance. In color it is largely the same as the 
fragment^, grayish or yellow, although the presence of pyrite in the 
rock may give rise to a red color over considerable areas. With 
increased amount of ash in the original rock, the soil becomes light 
gray in. color. 

THE ACID FINE-GRAINED TUFFS. 

The acid fine-grained tuffs occur interbedded with the slates and 
coarser tuffs. They have no extended areal distribution, but may 
be found in nearly all parts of the district in outcrops of limited 
size. On the one hand, they grade very gradually into the slates ; 
while on the other, they pass into the acid coarse tuffs. At times 
there are frequent alternations between the three in the course of a 
few yards, bespeaking a rapid change of conditions during their 
deposition. 



II THE CLD MINING DISTRICT OF DAVIDSON COUNTY. 

Macroscopic description. — The fine-grained tuffs are extremely 
dense, hard rocks, usually light in color; though, through small 
admixtures of organic matter, they may become dark colored or 
black. They have been silicified and consequently are very brittle, 
breaking with a conchoidal fracture into small, translucent chips and 
slivers of a very keen edge. They emit a clear, ringing sound when 
struck with the hammer. A light gray or cream color is the most 
common, though various shades of greenish-gray, and even dark 
gray or black, are not uncommon. Many specimens have a greasy, 
oily appearance upon fresh fracture. The harder, denser varieties 
of these rocks are locally called "gun-flints," and have been described 
as "whetstone slates" and "hornstones." 'These resemble very much 
a chert or novaculite. The texture varies from fine graular to dense, 
but even in the coarser facies, little or nothing can be told of the 
mineralogical content. Bedding planes are sometimes visible ; other- 
wise the rock is quite homogeneous. The greater number of out- 
crops have suffered little from mashing ; although some of the sericite 
schists, particularly in the vicinity of Silver Hill, show by their occa- 
sional gradation into the massive tuffs to have been derived from 
them. 

Microscopic description. — The microscope reveals a dense, crypto- 
crystalline groundmass, in which may be seen fragmentary crystals 
of quarts and feldspar, very rarely a fragment of another rock, and 
a host of other minerals, mostly secondary, in subordinate amounts. 

The quartz occurs in small fragmental crystals. It rarely shows 
good crystal outline : in such cases it has been recrystallized. Occa- 
sional particles have a moon-shaped contour, representing the inter- 
vening cell walls of a highly expanded pumice. 

The feldspar is both orthoelase and acid plagioclase, and is also 
fragmental in outline. It is usually clouded with kaolin, often to 
the extent of obscuring its nature. In amount it is subordinate to 
the quartz. Microline could be distinguished in one instance. 

Iron ore occurs in small grains, and at times in larger aggregates, 
from which a portion has been removed by solution. It is largely 
pyrite, of later age than the rock. 

Colorless garnets occur very rarely. 

Fragments are quite rare. In one or two instances small pieces 
of a rock composed of plagioclase laths were recognizable. 

The groundmass consists of a fine-grained mosaic of quartz and 






A DETAILED DESCRIPTION OE THE EOCKS. 45 

feldspar fragments, often knit together by sericite fibers. Present 
also are varying amounts of epidote and clinozoisite grains, patches 
of chlorite, calcite, kaolin, and rarely organic matter. 



Many of the fine tuffs under the microscope show no special tex- 
tural features. Where bedding planes are visible, they are due to a 
variation in size of material. An interesting feature in one slide 
is a normal fault in a bedding plane, with a throw of one-eighth inch. 
The resulting fissure is filled with epidote, quartz and calcite. 
Where the secondary minerals are abundant, there is a tendency for 
these to bend and wrap around the phenocrysts. If much sericite be 
developed, this material is apt to be arranged in definite lines. 

CHEMICAL COMPOSITION. 

A determination of the alkalies in one of the densest of the tuffs, 
which strongly resembled a chert, was made, with the following re- 
sult: 1 Na 2 0.22; K 2 3.54. 

The rock evidently has a fair feldspathic content. A complete 
analysis was not made, on account of the large amount of infiltrated 
silica. 

Classifiation, — The microscopic description and field relations 
of the rock indicate that it is a fine-grained tuff, of a rhyolitic or 
dacitic character. It is considered to be a volcanic ash, in part de- 
posited by water as indicated by the bedding planes, which has been 
indurated, highly silicified, and metamorphosed. 

Arenaceous phase. — Occurring one and one-half miles east of Fair- 
mont is a small area of a fine-grained, grayish-green, schistose rock, 
of an arenaceous nature. The rock is coarser than the ordinary fine 
tuff, so that its granular character can be seen with the eye. The 
microscope shows this rock to be a slightly coarser phase of the tuff, 
in which there is a good proportion of fair-sized quartz grains, some 
slightly rounded and others of a decidedly sherd-like outline. 

WEATHERING. 

The acid fine tuff, like the slate, has a varied mode of weathering, 
according to its degree of schistosity. The massive varieties, by 
virtue o f their numerous joint planes, are easily attacked by solu- 

wu 1 ^ arti A al analysis of acid fine tuff ('-gun-flint"), from Silver Hill, Davidson County, N. C. A S- 
Wheeler, Analyst. 



46 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

tions. As a result, the outcrops and loose "blocks are covered to a 
depth up to y 8 inch with a crust of yellow clay-like material, which 
mashes beneath the blow of a hammer. Small fragments and blocks 
become easily detached from the outcrops, and are so abundant where 
bands of the fine tuff cross the roads, that one on horseback could 
recognize the formation in the dark, by the ringing sound caused at 
each step by the iron horse-shoe striking the fragments. The result- 
ing soil is yellowish to grayish, and reveals its nature by the nu- 
merous chips of the parent rock which lie upon the surface. The 
schistose phases weather in a somewhat different manner, in that they 
tend to decay in place until they finally crumble into an ash-like 
material, perhaps quite similar in appearance to the original volcanic 
ash and dust which compose them. During this process the outcrops 
are often highly and beautifully colored, due to the degree of oxida- 
tion of the iron. This is especially true in places where there has 
been mineralization, so that the brilliant colors are often, and justly, 
taken as a guide in prospecting. 

THE ACID COARSE TUFFS. 

The acid coarse tuff has a widespread areal extent, second only 
to the slate. It forms bands of varying width, usually a mile or so, 
trending in a northeast and southwest direction. It also has a fre- 
quent occurrence within the belts of slate, where it is found in nar- 
row, restricted beds, often represented by a single outcrop. Its best 
development is just west of Mat Swamp Ridge, and in a badly 
mashed strip extending from Silver Hill to Conrad Hill. 

Macroscopic description, — The coarse tuff differs from the fine 
tuff in that its fragmental nature can always be recognized in a hand 
specimen. It is greenish-gray to bluish-gray in color ; its weathered 
surface is a kind of yellowish or neutral gray. This rock resists 
weathering much better than does the slate, so that its outcrops are 
always prominent. Upon close examination it is seen to be composed 
of a bluish or greenish matrix, whose nature can not be made out, 
in which are imbedded numerous easily recognizable feldspar 
phenocrysts. (Plate VII, A.) A diligent search always reveals 
a greater or less number of included rock fragments. These are 
frequently quite prominent, though rarely predominant. Some- 
times the rock seems to be made up entirely of groundmass and 
phenocrysts. The fragments vary in size up to % inch in diameter ; 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE VU 




91 









A. Hand specimen of the acid coarse tuff, fragments are small and subordinate 

TO THE DENSE GROUNDMASS. 




B. Photomicrograph of an acid tuff, Davidson county, n. c. 30 diameters; polarized 
light; showing the fragmentary character of the rock. 



A DETAILED DESCRIPTION OF THE ROCKS. 47 

where they are predominantly larger the rock is called a volcanic 
hreccia. The most abundant fragments are light colored, siliceous 
ones ; though fragments of slate and of a dark colored, basic rock 
may be occasionally seen. The rock is fairly brittle, but varies in 
this respect, depending upon the amount of silicification. Large 
areas of the coarse tuff are massive, while considerable extents of 
them have suffered different degrees of mashing. As a final result 
of metamorphism, they pass into sericite schists. 

Microscopic description. — Fifteen thin sections of specimens from 
all parts of the area proved the coarse tuff to be fairly uniform in 
character. All agree in showing fragmental phenocrysts of quartz, 
orthoclase, and acid plagioclase, together with fragments of one or 
more kinds, imbedded in a fine-grained matrix. (Plate VII, B.) 

Orthoclase is the most abundant phenocryst and occurs in sub- 
hedral to anhedral and fragmental crystals, usually of a brick-like 
or slightly elongated outline. The edges in many instances are 
somewhat rounded. Carlsbad twins are often seen. Occasional epi- 
dote and clinozoisite grains, rare prisms of apatite, and sericite fibers 
in cases where mashing has been effective, occur as inclusions. The 
alteration is to kaolin, which always gives to the mineral a dusty or 
cloudy appearance. The "basket" twinning characteristic of micro- 
cline sometimes occurs, and this seems to have been formed from the 
orthoclase by mashing, as only the schistose phases of the rock have 
this feature; and there is often a gradation from the microcline into 
the unchanged orthoclase. 

Plagioclase, as a phenocryst, is subordinate in amount to ortho- 
clase. It occurs in subangular, lath-shaped forms, whose extinction 
angles show it to be at the acid end of the series, hardly more basic 
than oligoclase. 

Quartz is usually in smaller amounts than the feldspars, and oc- 
curs in grains and aggregates of grains. It ordinarily has a frag- 
mental outline, though it sometimes shows a fair hexagonal form, 
due to recrystallization. There are certain areas which have the ap- 
pearance of shattered and recrystallized phenocrysts. Occasional 
undulatory extinctions may be seen. A few small anhedrons show 
embayments filled with groundmass. 

Biotite is frequently present in the form of shreds and sponge- 
like crystals of ragged outline. These show various degrees of al- 
teration into a pale green chlorite. 



48 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Iron ore occurs as small specks and grains. It is probably mostly 
pyrite. Associated patches of chlorite are sometimes seen. 

Fragments occur in all the sections, and in practically all cases 
are less abundant than the groundmass. They are angular in outline 
and consist of several kinds of rock. Most abundant are fragments 
of the acid fine tuff and slate; although there are often present 
fragments of a rock andesitic in nature. The latter type, under 
crossed nicols, shows itself to be composed of a mesh of striated plagio- 
clase laths of a medium acid nature, mixed with such secondary 
minerals as biotite, sericite, epidote and clinozoisite. Sometimes 
larger, striated feldspars occur as phenocrysts. With increasing 
number of andesitic fragments, the rock passes into an andesitic 
coarse tuff or breccia. There are probably also fragments of rhyo- 
lite present, but these can not be distinguished with certainty from 
the fine tuff. A type of fragment seen in one slide deserves special 
mention. It is composed of sponge-like biotite crystals and rounded 
areas of chalcedonic silica, shot full of slim, colorless needles of 
actinolite: it probably represents an amygdaloidal andesite. 

The groundmass consists of a dense mosaic of quartz and feldspar, 
with varying amounts of sericite, epidote, and clinozoisite. 
More or less of a finely granular, grayish-green, non-polarizing ma- 
terial, most probably kaolin or clay, is frequently associated. (Plate 
VII, B.) The common type of groundmass has a brownish-gray, 
clay-like appearance in plane light, and becomes almost dark between 
crossed nicols. 

TEXTURE. 

The absolute lack of order and regularity with which the com- 
ponents are thrown together is the most striking textural feature. 
In one slide a faint suggestion of bedding was noticed. Kather 
interesting is the fact that in some cases where the hand specimen 
shows a certain amount of schistosity, the microscope fails to reveal 
any mashing effects. 

Classification. — The microscopic details and field relations are 
considered sufficient to classify the rock as an acid coarse tuff. Its 
mode of origin and somewhat variable nature does not permit of 
such an accurate classification as would be possible with a rock which 
had solidified from a molten magma. It is largely, however, 
rhyolitic to dacitic in character and in rare cases it strongly sug- 
gests a tr achy tic character. It doubtless represents the explosive 



A DETAILED DESCRIPTION OF THE ROCKS. 49 

phases of the rhyolitic and dacitic flows exposed within the district. 
The term, therefore, will embrace all gradations between a trachytic 
and dacitic tuff: a finer distinction is impossible. 

WEATHERING. 

The mode of weathering of the acid coarse tuff depends largely 
upon the degree of mashing it has undergone. The massive varieties 
have the more distinctive mode of yielding to the attacks of the 
elements. The groundmass is less resistant than the fragments, and 
the result is that a bumpy surface is developed, caused by the frag- 
ments standing out from the matrix. This is so characteristic 
that it is possible to recognize the fragmental nature of the coarse tuff 
at a glance. The outcrops are large and prominent and are colored 
a dull yellow or neutral gray on the surface. (See Plate II, A.) 
The weathering is more mechanical than chemical, and the resulting 
soil is a grayish one, with no especially distinctive characteristics. 
The more schistose phases tend to become chemically altered, 
rather than mechanically disintegrated ; so that the badly mashed 
facies are highly colored, and indeed in many cases are indistinguish- 
able from the sericite schists resulting from the metamorphism of 
the fine tuffs. The mashed fragments tend to become ash-like and 
white: thus the fragmental nature of some of the mashed tuffs, not 
noticeable on fresh break, is brought out by weathering. 

THE ACID VOLCANIC BKECCIA. 

The acid volcanic breccia is a composite type based more upon 
macroscopic and field distinctions than upon microscopic differences. 
It includes two phases, alike mineralogically, but unlike in mode of 
origin ; and grading the one into the other in such a manner that no 
lines can be drawn upon the geologic map separating the two. On 
the one hand, the coarse tuff containing fragments predominant over 
groundmass and larger than y 2 inch in diameter is called a volcanic 
breccia ; on the other, the brecciated form of rhyolite, which im- 
perceptibly grades from a massive flow rock into a cemented mass 
of rhyolite fragments, and which is considered a rhyolite broken into 
angular fragments through flowage, is given the same name. The 
greater portion of the rock is characterized by the fragments pre- 
dominating over phenocrysts and groundmass. While no hard and 
fast lines can be drawn between the rhyolite or acid coarse tuff and 
the volcanic breccia, its delineation may be indicated with sufficient 
4 



50 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

accuracy to warrant its separation. It is characteristically developed 
along Flat Swamp Kidge, forming the main portion of this elevation. 

Macroscopic description, — The breccia, when typically developed, 
is easy to recognize. It is made up largely of light colored frag- 
ments, usually V 2 to 1 inch in diameter; though some were noted 
2 feet long. (Plate VIII, A.) A closer examination reveals these 
to be light greenish-gray to white in color, quite siliceous, and to 
contain an occasional feldspar phenocryst. There may also at times 
be seen fragments of other rocks, chief among which are small, ir- 
regular pieces of a dark, basic rock, composed of numerous biotite 
specks surrounding minute feldspar crystals. The groundmass is 
usually dark green or gray, and in it are found abundant small feld- 
spar phenocrysts. The breccia forms enormous rounded outcrops 
literally covering the ridges which they form. (See Plate III, A 
and B.) It grades into the rhyolite by containing smaller and 
fewer fragments, until the two become indistinguishable. At times 
the brecciated character can only be seen on the weathered surface. 
A type composed largely of fragments may show flow lines. 

Microscopic description. — The volcanic breccia under the micro- 
scope differs so slightly from the coarse tuff that a detailed descrip- 
tion will not be given. Phenocrysts of orthoclase, plagioclase, and 
quartz are as described under the previous rock. The groundmass 
differs little, if any, and the same secondary minerals are present. 




Fig. 2— Sketch of small glass sherds within a fragment of the volcanic breccia. 
Magnified about 88 diameters. 

In the breccia, however, a much greater amount of green biotite is 
developed, and the fragments are much more abundant. Fragments 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE VIII. 



■' '■ 










■-•' Mi^kssiM 












k ' • • : . 


s8w§^'' 




. 


...; : *■■¥ 


:;;,«:.;*; 






r 




: . J.;-','.'-'- 




If 


Wt&m 


'■'■■.' Kk 




















J..V 




■v- .:;■■:;' - v« : 


F .i,.^ <-?' : 


■ . ■ 








Hand specimen of the acid volcanic breccia from flat swamp ridge, it is made up of 
predominating light colored acid fragments over one half inch in 
diameter. a dark colored andesitic fragment may 
be seen in the center of the specimen. 




Small boulder of the acid volcanic breccia, showing a characteristic 
developed in weathering. 



SPONGELIKE SURFACE 



A DETAILED DESCRIPTION OF THE ROCKS. 51 

of the acid flows and tuffs are the most frequent. Occasional ande- 
sitic fragments may be seen, composed largely of biotite and plagio- 
clase. One fragment of acid nature is deserving of special note, 
for it contains fragments in the shape of shreds, that are so charac- 
teristic of explosive volcanic activity. (See figure 2.) This suggests 
the complexity of the volcanic activity, for here is evidence in one 
place of at least two outbreaks, with a long interval between. Flow 
lines are better seen in hand specimen than under the microscope. 
(See Plate IX, A and B.) 

Classification. — This rock from its 'field relations and microscopic 
make-up is considered to be largely rhyolitic in character; though 
becoming dacitic at times, and perhaps in rare instances trachytic. 
It is therefore called an acid volcanic breccia : this term is understood 
to include both coarse volcanic ejecta and the brecciated phase of 
rhyolitic lava flows. 



WEATHEKING. 



The volcanic breccia is but little jointed and quite massive, and 
resists weathering more readily than any other rock in the district, 
except perhaps the rhyolite. Consequently it forms prominent 
ridges and is found in enormous outcrops. These weather to a 
fairly smooth surface, with great concentric shells or plates at every 
stage of peeling off, many being ready to fall at the touch of the 
pick. In color these masses are a light gray, or particularly in the 
loose fragments, a dull dirty gray. The surface is at first fairly 
smooth, or only slightly pitted ; but the pieces which fall down soon 
become quite rough and present a surface very much like that of a 
sponge. (Plate VIII, B.) This sponge-like weathering, due to 
the weathering out of the fragments, as opposed to the reversed mode 
of weathering of the coarse tuff, in which the fragments stand out, 
is characteristic of the breccia, and particularly of that portion which 
had its origin through flowage. After the first peeling off of the 
concentric plates, the weathering becomes to a certain degree chemi- 
cal, and the final result is a grayish, sandy soil, filled with fragments 
and boulders of the original rock. Schistose phases are rare, but 
such as exist suffer the same changes that were described in the 
case of the mashed coarse tuff. 



52 THE CID MINING- DISTRICT OF DAVIDSON COUNTY. 

RHYOLITE. 

Flows of rhyolite have their best development along Flat Swamp 
Ridge, where they appear upon the surface in narrow strips, forming 
the highest portions of the ridge. More or less schistose phases of 
the same rock occur here and there within the area of acid volcanic 
breccia ; but in most cases these are represented by isolated outcrops 
and do not cover sufficient territory to show upon the geologic map. 
The rock in all its occurrences grades into a brecciated phase. 

Macroscopic description. — In hand specimen, the rhyolite is a 
dense, black, dark green, or grayish-green, porphyritic rock, with a 
greasy luster on fresh fracture. It is quite brittle and breaks with 
a conchoidal fracture; forming slivers with keen, translucent edges. 
The rock is not very porphyritic ; though it has a decidedly speckled 
or mottled appearance, which is due only in part to the phenocrysts, 
and more especially to the great number of loosened splinters which 
appear white and opaque by reflected light. The phenocrysts are 
uniformly distributed and may be seen to be elongated feldspar 
crystals of fair outline. Quartz phenocrysts are rarely present and 
are never prominent. Occasional small areas of dark green, chloritic 
material are visible, and sometimes specks and grains of pyrrhotite 
are prominent. Flow lines are developed in favorable places, but 
are best seen on weathered surfaces. (Plate X, A.) There are 
denser phases of the rock which are not apparently porphyritic and 
these may easily be confused with the silicified acid fine tuff. Part 
of the so-called "gun-flint" may be a very dense rhyolite. The aver- 
age rhyolite is massive and somewhat jointed; in a few places it has 
suffered some degree of mashing. Its brecciated phase is classed as a 
volcanic breccia. 

Microscopic description. — The microscope discloses phenocrysts 
of orthoclase, plagioclase, and quartz in a groundmass consisting of 
a pepper and salt mixture of quartz and feldspar. 

Orthoclase occurs as phenocrysts in fair sized crystals of subhedral 
to anhedral habit, with a tendency toward a brick-like form. These 
are usually twinned according to the Carlsbad law, and often the 
edges are slightly rounded. The crystals frequently have a sort of 
shattered appearance, and certain of them are fragmental. In a 
section of a metamorphosed phase of the rock, the orthoclase was 
observed to grade into microcline. Inclusions are occasional small 
patches of calcite, sometimes epidote and brown biotite, and more 



N. C. GEOLOGICAL AND; ECONOMIC SURVEY. 



BULL. 22, PLATE IX 




A. Photomicrograph of a fragment contained in the acid volcanic breccia, 

DAVIDSON COUNTY, N. C. 30 DIAMETERS; ORDINARY LIGHT J SHOWING 
FRAGMENTARY NATURE OF COMPONENTS. 




B. Same in polarized light, showing the angular and shred-like 

OUTLINE OF THE COMPONENTS. 



A DETAILED DESCRIPTION OF THE ROCKS. 53 

frequently shreds of sericite. The feldspar is in no case perfectly 
fresh, but shows partial alteration to kaolin. 

The plagioclase is somewhat subordinate in amount to the potash 
feldspars and occurs in smaller, subhedral crystals, which show albite 
twinning. Extinction angles prove these to be at the acid end of the 
series, and not more basic than oligoclase. They contain small in- 
determinable inclusions, and are partially altered to kaolin, yet on 
the whole appear fresher than the orthoclase. 1 The plagioclase, too, 
shows a certain amount of shattering. 

The quartz rarely occurs in well-defined phenocrysts, but usually 
forms masses which show themselves between crossed nicols to be 
aggregates of interlocking grains of various sizes. These probably 
represent granulated phenocrysts, and sometimes suggest some de- 
gree of recrystallization since granulation. There are frequently 
uniformly distributed smaller anhedrons ; and rarely a phenocryst of 
larger size with an embayment of groundmass may be seen. In some 
slides occur a certain amount of infiltrated chalcedonic silica, resem- 
bling spherulites. 

Iron ore is present sparingly in grains and cubes. It is repre- 
sented by both pyrite and pyrrhotite. 

Irregular shreds of a brown, pleochroic biotite are present, and 
are apt to be in aggregations rather than uniformly distributed. 

The groundmass is a fine-grained pepper and salt mixture of quartz 
and feldspar, containing a host of other minerals in variable but small 
amounts. Among them may be recognized irregular patches of cal- 
cite, areas of a pale green chlorite, occasional grains of epidote and 
clinozoisite, fibers of sericite, shreds of greenish biotite, and specks 
and grains of iron ore. Some kaolin is invariably present. 

Texture. — The rock is porphyritic, consisting of phenocrysts set in 
a groundmass which is microgranitic. Occasional flow lines are 
present, and these are usually rendered visible by the kaolin dust. 
No spherulites or lithophysse could be definitely recognized. 

!The orthoclase in older rocks is frequently muddier than the plagioclase; but from this it must 
not be concluded that the first weathers more easily than the latter, for the reverse is true. See 
Lemberg, J. Zur Kenntniss der Bildung und Umwandlung von Silicaten. Zeit. d. Deut. Geol. Ges.. 
v. 35 (1883): 575. 



54 



THE CID MINING- DISTRICT OF DAVIDSON COUNTY. 



CHEMICAL COMPOSITION. 



The chemical composition of the rhyolite is shown in column I of 
the following table. The analysis of a similar rock from the South 
Mountain district of Pennsylvania is included for comparison : 



ANALYSES OF RHYOLITE AND RE- 
LATED ROCK. 





I 




II 




a 


b 




Si0 2 


74.67 
10.78 
1.25 
2.11 
trace 
1.47 
5.31 
2.68 
0.59 
1.30 


74 .43 
10.69 

1.23 

2.U 

trace 
1.51 
5.47 

2.71 i 
0.63 L 
1.30 L 


73.62 


Ahos 


12.22 


Fe 2 3 

FeO 


2.08 
4.03 


MgO 


0.26 


CrO 


0.34 


N;. 2 0- 


3.57 


K2O 

H 2 


2.57 


CO2 


6'io 










Total 


100. 16 


100.16 


99.09 



I. Rhyolite from Flat Swamp Mountain, Davidson County, N. C. Duplicate analyses. J. E. 

P ° g II.' Devitrified S rnyoljte from South Mountain Pa. C. H Henderson, Analyst. Williams G. H., 
The volcanic rocks of South Mountain in Pennsylvania and Maryland. Am. Jour. Sci., v. 44 (1892), 
493, 494. 

The chemical analysis shows the rock to be a perfectly normal 
rhyolite. 

Classification,— All the features indicate that the rock repre- 
sents the devitrified remnant of an ancient rhyolitic lava flow. The 
rock is, therefore, classified a rhyolite or aporhyolite (devitrified 
rhyolite). 

Variation. — A type of rock whose nature cannot be accurately 
determined, but which is probably either a devitrified rhyolite or a 
highly silicified acid fine tuff, will be briefly described. This rock 
is of special interest, as it contains grains and masses up to % 
inch in diameter, of sphalerite, galena, chalcopyrite, and pyrite 
abundantly distributed without any seeming order or connection with 
lines of fracture. The rock occurs one mile northwest of the Em- 
mons Mine, just east of the road which leads past Beulah Church. 
A little prospecting has been done here. 

In hand specimen the rock is dark grayish-green, very dense and 
brittle, and breaks with a conchoidal fracture into chips with exceed- 
ingly keen edges. In addition to abundant areas of sulphides, there 
are thickly distributed minute white specks, suggesting incipient 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE X. 




A. Hand specimen of khyolite, showing flow structure made prominent by weathering, 

FROM FLAT SWAMP RIDGE, DAVIDSON COUNTY, N. C. 









; 




B. Hand specimen of a very dense and highly siliceous rock, containing abundant areas of galena, 

CHALCOPYRITE AND PYRITE. THE SMALL WHITE SPECKS ARE MINUTE AGGREGATES OF GRANULAR 

KAOLIN. THE ROCK IS EITHER A SILICIFIED TUFF OR DEVITRIFIED RHYOLITE. FROM 

ONE MILE NORTHWEST OF THE EMMONS MINE, DAVIDSON COUNTY, N. C. 



A DETAILED DESCRIPTION OF THE BOCKS. 55 

phenocrysts or crystals arrested in their development before taking 
on crystal outline. (See Plate X, B.) 

The microscope reveals no definite cine as to the nature of the 
rock. The white specks, in hand specimen suggestive of phenocrysts, 
are aggregates or bunches of granular kaolin. The groundmass is 
very dense and composed of quartz and feldspar, with chlorite, epi- 
dote, clinozoisite, biotite, and kaolin. The feldspars include both 
orthoclase and plagioclase. There are occasional areas composed 
largely of quartz, with subordinate amounts of feldspar, epidote, 
chlorite, and grains of the sulphides, having a sort of interlocking 
appearance as if the mass had undergone recrystallization. 

From the present evidence, no definite conclusions can be drawn as 
to the nature of the rock. If it be a rhyolite, however, it is of interest 
because containing such a variety and abundance of sulphides. 

WEATHEEING. 

Due to its dense and massive nature, the rhyolite is very resistant 
to the forces of weathering. Its outcrops are consequently found 
in the highest portions of the district. These are light gray, to almost 
white in color, because of a very thin film of decomposed material on 
the surface. This is very characteristic of the rhyolite (and of 
portions of the volcanic breccia). Occasionally flow lines may be 
visible on such surfaces, but are never prominently developed. The 
outcrops are usually rounded; sometimes they are angular due to the 
falling out of joint blocks. The final result of weathering is an 
arenaceous soil of light color. The rapidity of weathering is in- 
creased in the small portion of the rhyolite that has suffered 

mashing. 

DACITE. 

Dacite composes the hill east of Cid known as Kemp Mountain. 
It forms here an area of oval outline, about one mile long and % 
mile wide. 

Macroscopic description, — In hand specimen the dacite is a rather 
tough, grayish-green rock, with a slightly mottled surface. This 
is due to a few feldspathic phenocrysts and to specks and small 
patches of material resembling biotite and chlorite. Also small 
loosened chips on fresh fracture appear lighter in color than the mas- 
sive rock and add to this characteristic. The rock is quite mas- 
sive, little jointed, and occurs in numerous rounded masses, resem- 



56 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

bling the outcrops of rhyolite. A very close inspection reveals that 
many of the crystals resembling feldspar are green in color, probably 
due to an admixture of epidote. 

Microscopic description. — Under the microscope the dacite is seen 
to be composed of badly altered phenocrysts of feldspar, set in a fine- 
grained matrix of quartz and feldspar, together with patches of biotite 
and chlorite, and grains of epidote. 

The feldspar occurs in medium sized, badly altered phenocrysts 
of subhedral habit. Most of these are plagioclase, probably oligo- 
clase running into andesine. The crystals are often almost entirely 
replaced by epidote accompanied by some chlorite. Alteration is to 
kaolin and sericite fibers. 

Scattered through the rock occur patches of a green, pleochroic 
biotite, and areas of green chlorite, probably formed from the biotite. 
The two often appear identical in plane light, and are only distin- 
guishable in polarized light by the ultra-blue color of the chlorite. 

The groundmass is made up of grains of epidote, clinozoisite, and 
iron ores ; dust-like particles of kaolin ; sericite fibers, biotite shreds, 
and chlorite patches ; and a large number of quartz anhedrons mingled 
with elongated feldspar crystals. Quartz appears to be almost as 
abundant as feldspar, and is frequently found in crystals of fair 
rhombic outline, with occasional slight embayments around the 
edges. Similar dihexahedral quartz crystals, showing a rhombic 
cross-section, have been described by Klich 1 as occurring in the 
groundmass of a dacite from South America. 

Texture. — The rock is porphyritic, with a groundmass partaking 
of the character both of a microgranitic and pylotaxitic texture; 
microgranitic, because of a fine-grained mixture of quartz and feld- 
spar ; pylotaxitic, because composed of small feldspars with no glassy 
base. 

iKuch, Richard. Petrographie (from Geologische Studien in der Republick Colombia). 1892: 69. 



A DETAILED DESCRIPTION OF THE ROCKS. 



57 



CHEMICAL COMPOSITION. 

The chemical composition of the dacite may be seen in column I 
of the table. The analyses of two related rocks are introduced for 
comparison. 

ANALYSES OF DACITE AND RELATED 
ROCKS. 





1 


II 


III 


Si0 2 


72.33 
14.56 
0.15 
2.22 
0.91 
2.55 
3.40 
2.82 
0.30 
0.00 


74.57 
12.58 
2.77 
n. d. 
0.30 
0.35 
3.98 
3.70 
1.01 


69.96 


AI2O3 

Fe 2 03 

FeO 

MgO 

CaO 

Na 2 


15.78 
2.50 

n. d. 
0.64 
1.73 
3.80 


K 2 

H2O 

CO2 


4.12 
1.53 






Total 


99.24 


99.29 


100. 07 



I. Dacite from Kemp Mountain, Davidson County, N. C. A. S. Wheeler, Analyst. 

II. Dacite from Crimea, Russia. A. Lagorio, Analyst. Washington: Chemica analyses of 
igneous roclcs, U. S. G. S., Prof. Paper 11: p. 153. 

III. Dacite from McClellan Peak, Washoe, Nevada. F. A. Gooch, Analyst. Ibid.: p. 167. 

Classification. — Although there are present no quartz phenocrysts, 
the other features and the chemical analysis combine in placing the 
rock among the dacites. 

WEATHERING. 

The dacite weathers in a manner very similar to the rhyolite. It 
is very resistant and stands out in abundant rounded outcrops. The 
weathered surface is usually of a light gray or yellow color. This 
discoloration often extends for an inch or so inward from the surface, 
where a rather sharp line of demarcation from the fresh rock within 
is reached. The soil is a light colored, arenaceous one, not appre- 
ciably differing from the rhyolite soil. 

THE BASIC TUFFS, BRECCIAS, AND FLOWS. 

ANDESITIC FINE TUFF. 

A dense phase of the andesitic tuff occurs at only a few points 
amid the andesitic coarse tuffs and breccias. On account of its 
analogy to the acid fine tuff, it will be briefly described. 

Macrascopic description. — In hand specimen the fine tuff is a 
dense, massive, rather tough rock, breaking with an irregular frac- 
ture. In color it is greenish, though upon closer inspection the sur- 
face is seen to be a mottled mixture of epidote green and dull purple. 



58 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Barely with the unaided eye, and easily with the hand lens, a few 
very small feldspar phenocrysts may be made out. Numerous specks 
of pyrrhotite are distributed through the rock. 

Microscopic description. — The microscope shows the rock to con- 
tain a great number of ragged and broken feldspar crystals of small 
size, most of which show the albite twinning. A number of measure- 
ments showed these to be as basic as andesine. 

The groundmass is composed of an interlocking mass of plagioclase 
fragments, with a few grains of infiltrated quartz. Numerous small 
epidote grains, and occasional aggregates of kaolin and patches of 
chlorite are also present. More rarely seen are actinolite needles, 
and patches of black material which probably represent iron ore or 
organic matter. 

Classification.- — The microscopic details alone would not be suffi- 
cient to classify the rock with certainty. Its occurrence in the field, 
however, where it is found grading into the andesitic coarse tuffs and 
breccias, when considered in connection with the details given above, 
suggests strongly that the rock is merely a fine-grained phase of the 
andesitic tuff. 

WEATHERING. 

The fine tuff is only fairly resistant to the forces of weathering. 
It forms a sandpaper surface of rounded outline and greenish or yel- 
lowish color. The decay proceeds from the surface and cracks in- 
ward, accompanied by a discoloration of the rock. The soil is a 
reddish one, less arenaceous than the rhyolite soil. 

THE ANDESITIC COARSE TUFFS AND BRECCIAS. 

No distinction is made between andesitic coarse tuff and andesitic 
breccia, because the two types are too intimately associated to f be 
separately mapped. Under this combined heading, therefore, will be 
included all the dark colored and heavy andesitic rocks, whether mas- 
sive or schistose, which show in hand specimen a fragmental nature, 
an exception to this being some very badly mashed facies, which re- 
quire the use of the microscope to bring out their true nature. 

The andesitic tuffs and breccias are abundant rocks within the 
district. They form bands, usually a fraction of a mile in width 
and several miles in length, alternating with the belts of the other 
rocks. These rocks are most prominently developed along the south- 
west border of Flat Swamp Ridge and at several points near the north- 



A DETAILED DESCRIPTION OE THE ROCKS. 



59 



east edge of the district ; they form the elevated area just west from 
Bald Mountain; and in a mashed condition compose a ridge be- 
ginning a mile northeast of Silver Hill. A large number of occur- 
rences of smaller areal extent are found at numerous other points. 

Macroscopic description, — This andesitic fragmental rock varies 
greatly from place to place. Indeed the field variations are more dis- 
similar than are the thin sections when seen under the microscope. 
There are certain characteristics, however, which are common to all 
phases, and these will enable one in most instances to recognize the 
rock. 

In the first place, nearly all occurrences of the rock have a dark 
green color, almost an epidote green. But this color sometimes 
varies : on the one hand to a light grayish-green ; on the other, to a 
dark bluish-black. Prominent in all, save extremely schistose phases, 
is the fragmental nature of the rock. Often it is made up almost en- 
tirely of green fragments. Sometimes the fragments appear less 
abundant and subordinate to the groundmass ; at other times, they 
are quite small, and most of them have been converted into small 
areas of green, chloritic-looking material. In the extremely schistose 
phases the fragments can not be seen ; though even here they often 
become visible upon the weathered surface. The extreme toughness 
of the rock, far in excess of any other rock in the district, is a feature 
especially characteristic of the massive varieties, and useful in recog- 
nizing them. 

The typical massive phase of the rock may be described as fol- 
lows : dark green ; heavy ; tough ; composed almost entirely of green 
fragments one-fourth to three-fourth inches in diameter, some an epi- 
dote green, others darker; space -between fragments filled with 
irregular areas of feldspar phenocrysts mixed with greenish material 
resembling biotite and chlorite ; numerous small specks of pyrrhotite 
uniformly distributed ; occasional specks of chalcopyrite ; boundaries 
of fragments often indefinite. 

A less abundant massive phase has the following characteristics : 
heavy ; tough ; composed almost entirely of dark green fragments up 
to one-half inch in diameter ; space between fragments filled with 
irregular areas of white feldspathic material; occasional specks of 
epidote recognizable ; rare grains of pyrrhotite and chalcopyrite. 

A slightly mashed phase shows the following features: light 
grayish-green; fragments not prominent; contains small, irregular, 



60 



THE CID MESTIZO DISTRICT OF DAVIDSON COUNTY. 



dark colored areas apparently composed of chlorite; dark colored 
patches of calcite ; very rare feldspar phenocrysts, visible only with 
hand lens; occasional fragments of a siliceous rock. One specimen 
contains a fragment 3 inches in diameter of a dense, dark colored, 
siliceous rock. The fragment contains specks of pyrrhotite along cer- 
tain lines and in isolated positions, which have apparently derived 
their material from the fragment, as this had been bleached to a 
distance of one-fourth inch from each particle of iron ore. A pecul- 
iar mottled appearance is thus given the fragment. (See Plate 
XI, A.) A few specks of chalcopyrite occur with the pyrrhotite. 

An extreme degree of mashing converts the rock into a greenstone 
schist ; grayish-green to dark green ; highly schistose ; no fragments 
visible on fresh fracture ; fragmental nature sometimes brought out 
on weathered surface ; few specks of pyrrhotite. 

Microscopic description.— The andestitic tuffs and breccias pre- 
sent a more uniform appearance in thin sections than in hand speci- 
mens. The microscope reveals in most cases a preponderance of 
greenish fragments over feldspar phenocrysts and groundmass. 

The areas of groundmass form usually only a very small portion 
of the rock, and are irregular in outline, with frequent reentrant 
angles and curves, as they fill in between the jagged edges of the 
fragments. The high power shows these areas to be an interlocking 
mass of feldspar, mostly plagioclase (probably oligoclase running 
into andesine). The feldspars near the edges of the areas tend to 
arrange themselves at right angles to the contact lines, and needles of 
actinolite run from the fragments into the feldspar. In addition, 
these areas contain grains and prisms of epidote, and often sericite 
fibers and kaolin dust. In many sections shreds and patches of 
biotite and chlorite occur in the groundmass. 

In the few cases where phenocrysts of orthoclase are found between 
the fragments, these occur in subhedral to subangular forms, some- 
times having slightly rounded edges. Zonary structure and undu- 
latory extinction may be developed. Carlsbad twinning is also fre- 
quently seen. Inclusions are sericite fibers and shreds of biotite. 
The alteration product is kaolin. 

Plagioclase forms more abundant phenocrysts and is found in 
elongated, subhedral crystals ; also in ragged, angular, and rounded 
forms. These are sometimes bent and even faulted. Many show 



A DETAILED DESCRIPTION OF THE KOCKS. 61 

undulatory extinction and zonary structure. Sericite and kaolin 
occur as inclusions. 

Quartz may be seen in some of the sections occurring in anhedrons 
or hexagonal crystals, but in no place does it appear to be a primary 
constituent. Irregular areas of chalcedonic silica may less often 
be seen. 

Biotite of a brown-green color and strong pleochroism is frequently 
developed. The shreds occur around the fragments and phenocrysts, 
and sometimes even within the fragments. The biotite is considered 
secondary and to have been developed at the same time in both 
groundmass and fragments. Included rutile needles are occasion- 
ally present. 

Chlorite occurs in patches and is probably an alteration product 
of the biotite. 

Epidote, accompanied by some clinozoisite, occurs in grains and 
prisms. It is variable in amount ; in some sections it forms the 
greater portion of the groundmass. 

There is in some sections considerable amount of grayish-black, 
non-polarizing material, which occurs in areas and drawn out into 
lines which wrap about phenocrysts and fragments. This is in the 
main kaolin, and probably contains an admixture of organic matter. 
In other sections this material is of a gray color, here probably free 
from organic matter, and varies in amount present. 

The fragments are quite varied and will merit a rather detailed 
description. It will be understood that all types of fragments are 
not found in any one occurrence of the rock. 

Type 1. Andesitic fragment : composed of a mesh of plagioclase 
laths, some bent and twisted and some ragged and broken ; all have 
the same general alignment; accompanied by epidote, calcite, and 
much chlorite; porphyritic and contains a few subhedral plngioclase 
phenocrysts; actinolite needles present; kaolin and chlorite so ar- 
ranged in wavy lines as to suggest now structure. The fragment 
undoubtedly represents an andesitic flow rock, with a pylotaxitic 
groundmass of a fluidal texture. 

Type 2. Andesitic fragment: Same as type 1, but lacks trachytic 
arrangement of feldspar laths. Some of these fragments are packed 
full of actinolite needles. 

Type 3. Andesitic ( ?) fragment: Dark green; composed of a 
multitude of actinolite fibers and occasional irregular feldspar crys- 



62 



THE CID MINING DISTRICT OF DAVIDSON COUNTY. 



tals of indefinite outline, together with some epidote. This may rep- 
resent a more altered phase of type 2. 

Type 4. Amygdaloidal andesitic fragment: Contains numerous 
small, rounded or oval areas, usually filled with chalcedonic silica, 
biotite or chlorite, but sometimes filled with black material, prob- 
ably a mixture of kaolin and organic matter ; at times filled with 
grains of epidote and clinozoisite,- or calcite ; between the amygdules 
may be occasionally made out a feldspar lath, -showing faint albite 
twinning. (See PI. XI, B.) For the greater part the feldspars have 
been replaced by a veritable mesh of actinolite needles, which tend 
to be arranged at right angles to the amygdules and frequently run 
into them. This type of fragment is abundantly present in many 
of the occurrences. (See fig. 3.) 



P^V 


o _ ■*" 




8 ° 

V 

1 On 






yu 


ti 





Fig. 3. — Sketch showing the amygdules within an andesitic fragment contained in the an- 
desitic breccia. Magnified about 88 diameters. 

Type 5. Acid fragment: Difficult to determine, but is highly 
feldspathic, with but an exceedingly small quantity of secondary 
ferromagnesian minerals, such as epidote, clinozoisite, and chlorite. 
A small amount of kaolin and a few prisms, probably apatite, can 
also be recognized. Some of the feldspars show albite twinning, 
indistinctly developed. No quartz can be discerned with surety. 
The fragment is probably a piece of flow or tuff of trachytic character. 



TEXTURE. 



The rock has a typical fragmental character, in which rock frag- 
ments and broken feldspar phenocrysts are indiscriminately mingled 
in a fine-grained groundmass of a more or less pylotaxitic nature. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XL 







A. Hand specimen op andestic breccia with included acid fragments, the light colored streaks and spots 
in the fragments are "zones of growth" from which small specks of iron ore have evidently 
derived a portion or all of their material. 



' 




B. Photomicrograph of an amygdaloidal fragment contained in the 

ANDESITIC BRECCIA; 105 DIAMETERS; ORDINARY LIGHT. 



A DETAILED DESCRIPTION OF THE ROCKS. 63 

Very striking is the fact that certain phases of the rock, which appear 
schistose in hand specimens, fail to show this feature under the 
microscope. This is especially noticeable where the cavities of an 
amygdaloidal fragment have remained round or oval and show no 
signs of elongation, even though the rock may have had a considerable 
degree of schistosity imposed upon it. This indicates a period of 
sufficient length, subsequent to the formation of the vesicles and 
before the mashing of the breccia, to permit the infiltration and 
filling of the cavities; otherwise they could not have resisted the 
compressive force inducing schistosity. Some variations show the 
effects of mashing by the bending of the groundmass around the 
fragments, forming a kind of "augen" structure; and by the flat- 
tening and parallel alignment of the secondary minerals. In gen- 
eral, the amount of secondary material, such as epidote, biotite, 
chlorite, etc., increases with the degree of schistosity. 

CHEMICAL COMPOSITION. 

A partial chemical analysis of a typical specimen of the massive 
andesitic breccia is shown in column I of the following table. Part 
of an analysis of a similar rock is given for comparison. 



ANALYSES OF ANDESITIC BREC- 
CIA AND RELATED ROCK. 




I 


II 


Si0 2 -- 


50.07 
8.21 
3.05 
0.38 


52.35 


CaO 

NasO 

K2O2 


8.16 
3.17 

0.88 



I. Partial analysis of massive andesitic breccia from west of Bald Mountain, Davidson County, 
N. C. A. S. Wheeler, Analyst. 

II. Andesite from Siebengebirge, Prussia. (Analysis partially quoted.) Analyst not stated. 
Washington: Chemical analyses of igneous rocks, U. S. G. S., Prof. Paper 14: p. 285. 

The analysis given corresponds to that of a rather basic andesite. 

Classification. — The rock may, without question, be classified as 
andesitic in nature. Whether it be a mica-, augite-, or hornblende- 
andesite cannot be definitely stated. It very probably varies, how- 
ever, from an acid to a basic andesite, having no exact values 
within these limits. In certain instances the rock is transitional 
into an acid or felspathic phase of breccia, and some phases might 
more aptly be called trachy-andesites ; but such are grouped under 
the general heading. It may be that through a decrease in the 



64 THE CTD MINING DISTRICT OF DAVIDSON" COUNTY. 

number of andesitic fragments and the consequent increase in 
phenocrysts and ash of an acid nature, a transition into the acid 
series of tuffs and breccias is accomplished. Some occurrences in 
the field strongly suggest this. No specimens of the rock, however, 
appear to be more basic than a basic andesite. 

WEATHERING. 

The weathered surface of the fragmental andesite is quite dis- 
tinctive. In general the rock forms a bumpy or billowy surface of 
grayish, grayish-green, or brownish color. The bumps are rounded, 
without steep slopes, and often the entire surface has a sandpaper- 
like appearance and feel. A certain degree of schistosity accentuates 
these features ; the massive phases have them to a less degree ; the 
very -schistose phases likewise show them but to a limited extent. 
Frequently the surface may in addition have a sort of porous struc- 
ture, as if the more soluble portions of the rock had been removed. 

The original dark green color is due chiefly to chlorite, biotite, 
and epidote. The weathered surface assumes a grayish color in 
proportion as these constituents are decomposed and carried away 
by solutions, and the kaolin, resulting from the decay of the feld- 
spars, is left behind. The soil is argillaceous in nature, often form- 
ing a sticky clay. Its color varies through numerous shades of buff 
and red. Where the rock is richly mineralized with pyrite and 
pyrrhotite, as is the case near Bald Mountain, the soil is a bril- 
liant red. 

The contour of the weathered outcrop is a good criterion of its 

degree of schistosity. Massive phases form rounded outcrops of a 

variety of shapes, which are never very narrow or elongated. 

Schistose varieties form narrow, elongated outcrops, resembling 

cockade hats. 

ANDESITE. 

The flow andesite does not have a wide distribution within the 
district. Its best development is a narrow band, crossing the Fair- 
mont-Denton road near the Mountain Schoolhouse ; and a broader 
area upon the southwest end of Three Hat Mountain. 

Macroscopic description. — There are two distinct phases of the 
rock; the one amygdaloidal, the ether massive; each of which is 
characterized by a green color and great toughness. The latter, of 
course, lacks the oval and rounded cavities, usually filled with green- 
ish material, which are characteristic of the former. 



A DETAILED DESCRIPTION OF THE KOCKS. 65 

The amygdaloidal phase is an epidote green rock, abundantly 
dotted with rounded and elliptical spots, varying in diameter up to 
4 mm. These are the amygdules and are filled with material of a 
darker green color, which appears in most cases to be epidote with 
chlorite, but sometimes in part calcite. The groundmass is so dense 
that nothing of its content can be made out with the unaided eye. 
Near the surface the material filling the cavities has weathered out, 
giving the rock a honey-combed appearance. (See Plate XII, A.) 

The massive andesite in hand specimen presents certain charac- 
teristics which render it easy of identification. It is a fine-grained 
rock, varying in color from a grayish-green, or epidote green mottled 
with blue, to a dark bluish-purple. All variations contain small 
green specks and masses of epidote. Except in the densest speci- 
mens, the rock is easily seen to be porphyritic ; the phenocrysts are 
feldspar laths of variable abundance. Upon close scrutiny the 
striated character of the crystals may often be seen. The nature of 
the dark green groundmass can not be determined, even with the 
aid of the hand lens. In one specimen the epidote is so arranged 
in lines as to give to the rock a banded appearance, suggestive of 
flow structure. The andesite occasionally contains minute grains 
and crystals of pyrrhotite. 

Microscopic description, — The microscope shows the amygdaloidal 
andesite to be composed of the following minerals: plagioclase, bio- 
tite, chlorite, epidote, calcite, clinozoisite, actinolite, and iron ore. 

Plagioclase is porphyritically developed in the form of a few 
subhedral crystals of slightly larger size than the feldspars of the 
groundmass. It is extremely abundant in the groundmass, where 
it occurs as small, slender, badly altered laths, with poor crystal out- 
line. Around these and binding them into a confused aggregate are 
fibers of a pale green actinolite. Albite twins are abundant, but 
accurate measurements can not be obtained. Such as could be made 
showed the feldspar to be hardly more basic than andesine. Inclu- 
sions are indeterminable; the product of alteration is kaolin. The 
feldspar is not found within the amygdules. 

Biotite is abundantly present within the amygdules, and is of an 
olive green color, strongly pleochroic. It occurs in shreds which are 
grouped in some instances in the interior of the amygdules ; in other 
instances they line the walls. They have no definite orientation, 

5 



66 THE OID MINING DISTRICT OF DAVIDSON COUNTY. 

either in respect to the walls of the amygdules or to one another. 
Biotite is not present in the body of the rock. 

A pale green chlorite occurs in abundance in the amygdules, and 
sparingly in the groundmass. It is of a scaly nature, and often 
between crossed nicols the field is at no time black, but a brownish 
color, due to a compensation between the confused aggregate of edges. 
Frequently also the mass appears essentially isotropic, caused by its 
excessively fine division. In the amygdules the chlorite occurs in 
the center, or lining the walls, or even at times filling the en- 
tire cavity. 

C al cite is an abundant constituent of the amygdules, and occurs 
either in association with the other minerals, or alone filling the 
cavity. It shows polysynthetic twinning parallel to (0112). 

Epidote and clinozoisite occur both in the amygdules and in the 
groundmass. Within the amygdules there is an abundance of clino- 
zoisite, showing an abnormal blue interference tint, together with a 
lesser amount of epidote with higher birefringence. Often the same 
crystal will show a gradation from the higher colors of the epidote 
into the ultra blue of the clinozoisite, and this gradation is usually 
from within outward. The two minerals are indistinguishable in 
plane light. They have usually a well-defined crystal outline and 
frequently twinning parallel to (100) may be seen. Also a cleavage 
parallel to (001) is well developed, often meeting at an angle in the 
twinned portions; a second cleavage parallel to (100) is often dis- 
tinct. The crystals are elongated parallel to the b-axis, and cross- 
sections of these are abundant. Epidote and clinozoisite may be 
grouped about the edges of the amygdules or may occupy the interior 
. of the cavity. Grains of these minerals are present in the 
groundmass. 

Iron ore is very sparingly present within the amygdules, occur- 
ring in small, irregular grains, usually associated with the chlorite 
or biotite. It is also present in small specks in the groundmass. 

The groundmass is composed of a confused aggregate of plagio- 
clase laths, bound together by numerous shreds and needles of actin- 
olite. Abundantly interspersed through this mass are small grains 
and crystals of epidote and clinozoisite, and an occasional small mass 
of chlorite. 

The massive rock contains essentially the same minerals as the 
amygdaloidal variety. Plagioclase is abundantly present as pheno- 
crvsts of a tabular, subhedral habit, with an occasional slender lath 1 



A DETAILED DESCRIPTION OF THE ROCKS. 



67 



shaped form. The variety is basic oligoclase, running into an- 
desine. A certain amount of infiltrated quartz is present, filling 
areas between the minerals. Epidote, with associated clinozoisite, 
occurs in rather large, irregular masses which are not uniformly dis- 
tributed; and as small grains or granules. Biotite is abundantly 
scattered throughout the sections. It occurs filling in between feld- 
spars and often forms areas about them. A small quantity of iron 
ore is also present. The groundmass is a fine-grained aggregate of 
epidote, plagioclase, iron ore, and probably sericite fibers. 

Trachytic variation. — In two occurrences of the rock just de- 
scribed — a fine-grained phase forming a small hill about 1 mile west 
from Three Hat Mountain, and a porphyritic phase occurring east 
of Kemp Mountain — small quantity of orthoclase could be recog- 
nized. In the fine-grained occurrence, this was mostly represented 
by microcline showing its characteristic "grating" structure. In 
other respects these rocks, though badly altered, were andesitic. 
They very probably represent a trachytic phase of the andesite, and 
perhaps might properly be called trachy-andesites. 

TEXTURE. 

The massive rock is typically porphyritic, with a groundmass of 
pylotaxitic texture. The amygdaloidal phase has also a pylotaxitic 
groundmass. 

CHEMICAL COMPOSITION. 

The chemical composition of the massive andesite is shown in 
column I of the following table. The analyses of several related 
rocks are included for comparison. 

ANALYSES OF ANDESITE AND RELATED ROCKS 





I 


II 


III 


IV 


SiO* 


66.21 
10.62 
6.44 
2.12 
0.94 
3.22 
6.11 
1.71 
0.61 
1.48 


66.28 
10.62 
6.41 
2.11 
1.15 
3.17 
6.09 
1.73 
0.61 
1.47 


65.58 
15.79 
0.94 
2.44 
1.47 
3.08 
2.58 
5.67 
1.16 


59,24 
13.84 
5.46 
1.36 
4.79 
5.60 
3.13 
4.22 
2.02 


60.41 
16.88 


A1203 


Fe 2 3 


FeO„ 


~"~6.~07 
2.82 
5.93 
6.72 
1.02 


MgO 


CaO 


Na 2 


K2O 


H 2 


CO2 












Total 


99.46 


99.64 

















analyse^L^ToguT jf AnaVsf ° f ^^ ^^ DaVidS ° n C ° Unty ' N " C ' ^plicate 
analy^olS^ A » a1 ^ Washington: Chemical 

Lbid}\, | 2 r 3 achy " andesitic breccia from Highwood Mountains, Mont. Hurlbut and Barnes, Analysts. 
teinsllhrt m p h 306 le andesite from Panama - Analyst not stated. Rosenbusch: Elemente der Ges- 



68 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

It is seen that the rock is chemically related to the three types 
given above. The small percentage of alumina present is noticeable ; 
this indicates a magma low in that compound. The relation of the 
alkalis is the strongest andesitic character brought out by the 
analysis. This will tend to place the rock among the andesites, 
although it has a strong alkalic caste. 

Classification.. — From a strictly chemical viewpoint, the rock is so 
alkalic that it might be called a trachy-andesite, or even a trachyte, 
with perhaps as much propriety as an andesite. But in the natural 
classification, where so much depends upon the nature of the feld- 
spars, the fact that orthoclase is subordinate to a plagioclase running 
as basic as andesine renders the rock more properly an andesite. 

It is recognized that the andesitic flows and breccias tend to be- 
come alkalic and trachytic in nature. In view of this, it would 
not be surprising if further work in other portions of the " SI ate 
Belt" should show up flows of typical trachyte. 



WEATHEKING. 



The andesite is fairly resistant to the forces of weathering, but 
not to such an extent as the acid flows and breccias. It yields more 
readily to chemical than to physical alteration, so that concentrically 
weathered boulders and outcrops of a brownish, grayish, or dirty 
yellow exterior are formed. The surface of the massive phases 
often has a rough, granular appearance and feel, comparable to 
coarse sandpaper. In the amygdaloidal phases, the filling of the 
amygdules is readily removed, so that the surface assumes a cellular 
or honeycombed structure which is quite distinctive. The outcrops 
of either variety are usually small; where jointing is developed 
small, rounded boulders abound. The soil resulting from the com- 
plete alteration of the andesite is a more or less arenaceous clay, 
which is characterized by a reddish color. 

DIKE KOCKS. 

- Gabbro and diabase are prominent within the district in the form 
of dikes. Gabbro is older than diabase, but younger than the other 
formations which it cuts. The diabase is of Triassic age. 

GABBKO. 

Gabbro occurs abundantly throughout the district as enormous 
dikes, trending in a northeast-southwest direction. These are al- 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XII. 




A. Hand specimen of the amygdaloidal andesite. the amygdules may be plainly seen with 

A HONEY-COMED MODE OF WEATHERING. 




B. Large rounded boulders of gabbro where a gabbro dike crosses the fairmont- 

DENTON ROAD ONE MILE NORTHWEST OF HEALING SPRINGS, DAVIDSON COUNTY, N. C. 



A DETAILED DESCRIPTION OF THE ROCKS. 09 

ways in conformity with the schistosity and their introduction seems 
conditioned by this easy line of yielding. The rock shows upon the 
surface in the form of large and small, rounded, yellowish boulders, 
distributed in lines following the direction of the dikes. (Plate 
XII, B.) 

Macroscopic description. — In hand specimen the gabbro appears 
a greenish-gray, massive rock, varying according to the locality from 
a medium fine grain, in which the component minerals are distin- 
guished with difficulty, to a medium coarse grain, in which crystals 
of green hornblende are easily recognized. The average rock is seen 
to be composed of a light green f erromagnesian mineral, - with a 
satiny luster, surrounded by white, opaque feldspar. With the hand 
lens, and in the coarser specimens, with the naked eye, the crystal 
faces of the green mineral may be plainly seen, and in favorable 
places its fibrous nature becomes apparent, while the feldspathic con- 
stituent fails to reveal definite outline. The rock is extremely 
tough, being knit together by its fibrous constituents^ but is moder- 
ately soft, so that when an edge is struck with the hammer it inclines 
to mash to a whitish mass rather than to flake off. 

Microscopic description. — In addition to the feldspar and fibrous 
hornblende, the microscope reveals epidote, clinozoisite, iron ore, 
chlorite, sericite, etc. 

The feldspar is too badly altered to admit of its determination. 
It has completely changed into a confused aggregate of grains, scales, 
and fibers ; among which may be clearly recognized grains and crys- 
tals of epidote and clinozoisite and fibers of uralitic hornblende. 
Sericite and kaolin are probably present, but cannot be determined 
with certainty; and other secondary products may be included. This 
alteration of the feldspar is that of saussuritization, and only an occa- 
sional outline of a feldspar lath remains to indicate its former pres- 
ence. The feldspar is considered to have been rich in lime to give 
the products mentioned above. 

The chief ferromagnesian mineral is a hornblende, which is rep- 
resented by the pale green, faintly pleochroic, fibrous variety known 
as uralite. This occurs in slender needles, having either a parallel 
or nearly parallel arrangement, or forming an interlocking mass, 
which becomes at no time dark between crossed nicols. There are 
also massive crystals of a pale green hornblende, which do not show 
a fibrous nature, but which are probably made up of closely packed 



70 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

bunches of uralite fibers. These often show twinning parallel to 
the front pinacoid (100), and at times several twinned lamellae may 
be seen in the same crystal. These massive crystals, like the fibrous 
ones, lack good crystal outline, and string out into the saussurite. 
The hornblende is considered largely, if not entirely, a secondary 
product from pyroxene. 

The iron ores occur in a few widely scattered brownish to black 
grains, most of which are partly, and some entirely, altered to leu- 
cozene. They may be either ilmenite or titaniferous magnetite. 

The epidote and clinozoisite occur with gradations, the one into 
the other ; frequently the same grain is part epidote and part clino- 
zoisite. The two are abundantly scattered througout the sections; 
their more usual occurrence is in the shape of irregular grains, 
although a prismatic form is not uncommon. The moderately high 
birefringence of epidote and the two abnormal interference colors of 
clinozoisite serve to distinguish the two. 

A small amount of calcite is present in irregular patches, with 
which is associated occasional masses of chlorite of a pale green color, 
scaly nature, and low double refraction. 

TEXTURE. 

The gabbro is essentially a mixture of saussurite and uralite, in 
which fibers and crystals of uralitic hornblende are imbedded in a 
mass of saussuritized feldspar. The age relations of the components 
need not be noted, since they are formed from previous constituents, 
whose relative ages are of course obscured by the result. For the 
same reason no special textural characteristics of gabbro are seen. 

Classification. — Although the rock is completely altered from its 
original state, its field occurrence, macroscopic and microscopic fea- 
tures render it safe to classify it as an altered gabbro. 

WEATHERING. 

The abundant jointing in the gabbro allows the easy access of 
solutions, and concentrically weathered boulders are readily formed, 
which are found both loose and imbedded in the surrounding soil. 
Their surface is a yellowish, more or less pitted one, composed of 
clay-like material stained by iron oxide. The outer rim of this ma- 
terial varies in thickness through various small fractions of an inch, 
and beneath this there is a gradation into a mass of a lighter color, 



A DETAILED DESCRIPTION OF THE ROCKS. 71 

which shows the interlocking fibrous structure of the ferromagnesian 
minerals from between which the feldspathic constituents have 
departed, leaving somewhat of a porous structure. The inner rim is 
not so thick as the outer and in turn grades into the normal rock 
beneath. The process of weathering carried further gives a slightly 
porous, yellow, clay-like mass, of rather firm constituency and little 
grit, called locally "soapstone," and which has been dug at a number 
of places for use as linings to fireplaces, and is said to have been 
shipped to Gold Hill and Silver Hill for use as furnace linings. The 
final product of weathering is a yellowish to a rusty red, more or less 
plastic clay, with little grit. At times in road cuts, ravines, and the 
like, this retains the original jointing of the gabbro. 

diabase. 

Diabase forms narrow dikes uniformly, though not abundantly, 
distributed throughout the district. It shows upon the surface as 
narrow lines of rounded boulders of an iron rust color, which indi- 
cate the trend of the dikes. It is the youngest rock in the district, 
for it cuts the other formations, including the gabbro. Moreover, 
it is considered of Triassic age, as dikes of a similar rock are found 
on the edge of the "Slate Belt," cutting both slates and Triassic 
sandstone. 

Macroscopic description. — The diabase is a massive, fine-grained, 
dark blue rock, with a faint purplish tinge and a more or less waxy 
luster. To the unaided eye it appears a closely knit aggregate of 
dark colored minerals, showing numerous small crystal faces. With 
the hand lens it is possible to recognize occasional striated feldspars, 
and to distinguish from these the darker colored ferromagnesian 
minerals. The olivine and augite, however, cannot be separated. 

Microscopic description, — The microscope reveals the following 
minerals, named in the probable order of their formation: iron ore, 
olivine, plagioclase, augite. (See Plate XIII, A and B.) 

The feldspar is basic labradorite, probably running into bytownite, 
and makes up about 45 per cent of the rock. It occurs in long, slen- 
der laths of subhedral habit. The albite twinning is universal, in 
combination with which is occasionally found a Carlsbad twin. 
Zonary structure is not pronounced. Inclusions consist of small 
particles of iron ore and rare shreds of biotite. In the sections 
examined the feldspars were quite fresh. 



72 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Augite, the most common ferromagnesian constituent, forming 
about 35 per cent of the rock, is of a pale green color and non- 
pleochroic. It rarely shows crystal outline, but surrounds and en- 
closes the feldspars, forming a matrix in which the feldspars are 
arranged at random. Iron ore is found as inclusions, and the altera- 
tion product, of which there is little, is a pale green, scaly mineral, 
probably antigorite. 

Olivine is present to the extent of about 17 per cent, an unusually 
large amount, and forms rounded crystals or grains of a very pale 
color. It includes particles of iron ore, and upon weathering forms 
what appears to be talc, rather than serpentine, the more common 
alteration product of olivine. This mode of weathering differs from 
the more usual form, in that the weathering is not confined to the 
cracks of the mineral with the segregation of iron ores, but pro- 
ceeds independently of cracks and is not necessarily accompanied by 
iron ores. 

The iron ores are abundantly scattered through the rock, but pre- 
fer the company of the ferromagnesian minerals, particularly olivine. 
They occur in both grains and specks, and rarely show good crys- 
tal outline. 

TEXTURE. 

The diabase is an excellent example of the ophitic texture: i. e., the 
long, slender feldspar laths are arranged at random, moulded around 
which is the augite, in most cases without definite crystal outline. 
The olivine mostly holds its own form against that of the feldspar, 
but in some cases it includes or partly includes a feldspar lath. Thus 
it appears that the olivine in part crystallized previous to the feld- 
spars and in part the crystallization was simultaneous. The sections 
show that the rock has suffered but an insignificant amount of 
alteration. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XIII. 






->- 







'; 


^* ; ' V * J V ;'C% 






• ■ ... 1^* " • 


^1 


wteBiL 


v - 




* 1 .*W* 


~:y- »""„> - ..-J ■>-• 


aJMtor' 


' ?^» '»»M 


** 




•. ; 


f 




... 



'M 



:k- 



" 



H . 



Photomicbograph OF DIABASE, DAVIDSON COUNTY, N. c. ; 30 diameters; 

AUGITE, OLIVINE, PLAGIOCLASE AND MAGNETITE, OPHITIC 
TEXTURE. ORDINARY LIGHT. 




B. Same in polarized light. 



A DETAILED DESCRIPTION OF THE ROCKS. 



73 



CHEMICAL COMPOSITION. 



The chemical composition of the diabase is given in column I of 
the following table. In column II the composition as calculated 
from the mode is given. The analyses of two related rocks are in- 
cluded for comparison. 



ANALYSES OF DIABASE AND RELATED 
ROCKS. 





I 


II 


III 


IV 


Si0 2 - 


47.66 
19.24 
1.83 
8.67 
10.79 
9.91 
1.14 
0.26 
0.06 


46.4 
18.1 
1.3 
7.7 
12.1 
12.8 
1.5 


46.63 
14.40 
2.85 
8.06 
7.25 
9.28 
2.47 
0.70 


45.80 


AI2O3 


18.49 


Fe203 


4.90 


FeO 

Mgo 

CaO 


5,67 
5.75 

12.70 


Na 2 

K2O 


3.20 
0.60 


H 2 












Total 


99.56 


100.0 













I. Chemical analysis of diabase from near Fairmont, Davidson County, N. C. A. S. Wheeler, 
Analyst. 

II. Microscopic analysis of the above specimen. J. E. Pogue, Jr., Analyst. 

III. Chemical analysis of diabase (auvergnose), Mt. Ascutney, Vt. W. E. Hillebrands, Analyst, 
Washington. Chemical analyses of igneous rocks, U. S. G. S., Prof. Paper, 24: p. 329. 

IV. Chemical analysis of diabase, Sudharz, Germany. O. Schilling, Analyst. Roth, Justus. 
Bietrage zur Petrographie der plutonischen Gesteine (1873): p. 22. 

The determined and calculated compositions shown in columns I 
and II are in fair accord. These also agree pretty well with the two 
analyses given for comparison. The most important point of differ- 
ence is the magnesia present. The greater percentage in numbers 
I and II is accounted for by the presence in them of an unusually 
large amount of olivine high in MgO. 

Classification. — The rock exhibits all the properties of an olivine- 
diabase, and it is classified as such. 



WEATHEEING. 

The diabase resists weathering as well as any rock in the district. 
It forms, however, concentrically weathered boulders with a yellow 
or rust-colored exterior. This coating of clay-like material stained 
with iron oxide is only a very small fraction of an inch in thickness 
and beneath is revealed the fresh rock. The soil resulting from the 
complete decomposition of these boulders is a yellow or rust-colored 
clay with very little grit. 



CHAPTER IV. 

PHYSIOGRAPHY. 
INTRODUCTION. 

North Carolina is naturally divided into three physiographic 
belts or provinces : to the east, the flat lying Coastal Plain ; to the 
west, the mountainous Appalachian Region; and between these, in- 
termediate in elevation, the Piedmont Plateau. The last contains 
the district under consideration. 

This area in general presents the surface features common to the 
Piedmont Plateau. It is a region of mature topography, with well 
rounded hills, gently sloping valleys, and graded streams ramifying 
into a network of streamlets that leave no portion of the area un- 
drained. Locally there are exceptions to the above statements, such 
as narrow ridges with steep, rocky slopes, and valleys with gorges 
and courses of rapids. 

BELIEF. 

The lack of a topographic map renders the description of the ele- 
vations only approximately correct. The survey of a proposed rail- 
road to be built parallel to the Yadkin River, which forms the south- 
west boundary of the district, gives a few accurate points, however, 
which will serve as a basis for the approximations. 

The elevation in the road near Yon Cannon's store at Fairmont 
is 645 feet above sea level. The northwest bank of Abbott's Creek, 
near the crossing of the Fairmont-Bringles Perry road, is 595 feet. 
The surface of ordinary water in Flat Swamp Creek, at a point 
about 100 feet from the edge of the river, is 576 feet. The summit 
of a saddle-shaped depression about seven-eighths of a mile south of 
Jacksonhill and on the road to Stokes Ferry is 689 feet. 1 The range 
of elevations within the district is estimated to be about 200 feet. 
This range may be encompassed by long, almost imperceptible slopes, 
undisturbing the general appearance of subdued relief; or by sud- 
den rises, with rugged topography as a result. 

The most striking feature of the entire area is Flat Swamp Ridge 
(PL I.) Rising abruptly from the Yadkin River to a height of 

x For these figures acknowledgment is due Mr. O. H. P. Cornell, Chief Engineer of the Winston- 
Salem Southbound Railway Company. 



PHYSIOGRAPHY. I 

about 200 feet, and extending as a narrow ridge for nearly 7 miles 
in a northeast direction, it forms a natural barrier, crossed by few 
roads. It divides the district almost equally, and, since it is visible 
from nearly all points, will serve as a kind of datum point to which 
the other surface features may be referred. 

A narrow road finds scant room around its southern end, between 
the river and the precipitous rocky ascents up to Flat Swamp Moun- 
tain. This name is given to that portion of the ridge which extends 
with a wavy crest for about 3^ miles to Healing Springs, where it, 
becomes sufficiently subdued for a road to cross. A half mile of 
small eminences brings the ridge to another depression, from which 
there rises Grice Mountain, of conical outline, with steep slopes on 
all sides. This is in turn succeeded by a narrow ridge of less height, 
known as Surratt Mountain, which dies out in the course of a mile 
or so in a country more generally hilly than that near the river. 
At any point, save in the depressions which are used to advantage 
for roads, it is difficult to cross. Enormous rocks rising tier upon 
tier often present sheer precipices of stone. Upon the eastern slope 
of Flat Swamp Mountain especially is this the case. The western 
slope is more gentle for a third of the ascent, when a sort of terrace 
is reached, which leads to the steeper portion. Upon this terrace 
there are a number of smaller elevations, forming ridges subordi- 
nate in extent to the main ridge. 

To the east from the top of Flat Swamp Mountain is presented 
a bird's-eye view of a low lying country, appearing from this height 
quite flat. Several miles distant, beginning beyond the confines of 
the present area and extending as far as the eye can reach, rise many 
ridges, separated by valleys of rolling country. Descending from 
the hill and going eastward, one finds a country of but little relief 
for a mile or so, until there appear a few rounded hills and a few 
low, mound-like ridges. In the extreme southeast corner of the area, 
near Lick Creek Church, the land begins to rise by gentle ascents. 
A little used road leads around near the Yadkin River and to an 
elevated plateau-like area, from which there is a splendid panoramic 
view of the entire Gold Hill country. Just to the east rises Bald 
Mountain, a pointed hill like an inverted cone, of about the same 
elevation as Flat Swamp Mountain. 

To one going west from Flat Swamp Mountain, the difference 
between valley and ridge is not decided. The region is made up of 



76 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

long, gentle slopes, forming well rounded, almost imperceptible di- 
vides between broad valleys. In such a type of country Fairmont 
and Silver Hill are situated. 

The portion of the area 10 miles or so removed from the Yadkin 
River becomes pre-eminently a region of ridges and rounded hills, 
to which the stretches of level country are much subordinate. The 
ridges here, like Flat Swamp, have a northeast trend, but none con- 
tinue for long distances, and many have little, if any, elongation. 
Three Hat Mountain, the most prominent of these ridges, has its 
beginning a few miles northwest of Cid, and extends beyond the area 
mapped. It is composed of three elevations, in nearly a north-south 
alignment, connected by saddle-like depressions, and resembling the 
crowns of three derby hats ; from which resemblance the name was 
probably suggested. Just to the west of Three Hat Mountain is a 
rather prominent ridge, to which no name has been given. A mile 
northeast of Cid, Kemp Mountain rises gently, with a steep descent 
toward Lick Creek. Viewed from the latter point, it appears a nar- 
row ridge ; seen from near Cid, it seems a less striking elevation. 
Just off Ihe area beyond Kemp Mountain begins a series of narrow 
ridges, rising to a height of several hundred feet. 

Summary. — There is an intimate relation between the surface 
configuration and the nature of the underlying rocks. An examina- 
tion of the ridges reveals that these without exception are composed 
of harder and more resistant rock than are the lower country and 
valleys. In a word, the geology and topography are in agreement. 
Hence it is believed that the present surface configuration is the 
direct result of the ordinary processes of weathering which are now 
going on, and by virtue of which the least resistant formations have 
been eaten into, and the harder ones thrown into relief. 

DRAINAGE. 

The Yadkin River is the master stream which receives the drain- 
age of the area. It crosses the region from northwest to southeast, 
cutting through hard and soft formations alike. It has found even 
Flat Swamp Ridge no barrier and has formed through it a narrow, 
V-shaped passageway. That the river was present long before Flat 
Swamp Ridge was brought into relief by the carving action of the 
elements seems an inevitable conclusion. Hence we call the Yadkin 
an antecedent or superimposed stream. 



PHYSIOGRAPHY. 77 

Of quite a different order are the principal streams that directly 
drain the district. Unlike the Yadkin, these conform to the under- 
lying rock formations ; finding it much easier to carve their valleys 
in the slate and mashed tuffs than in the harder breccias and flows. 
Unable to cut through ridges, they remain parallel and flow in a 
southwest direction. These, therefore, may be called consequent 
streams, as they have been developed in consequence of the underly- 
ing rocks. Abbott's Creek, Flat Swamp Creek, Lick Creek, and 
Cabin Creek are the important streams of this kind. 

Flat Swamp Creek is the largest of the four. It enters the area 
already a fair sized stream, and when it flows into the Yadkin it is 
30 to 40 feet in width. It varies greatly in the amount of water it 
carries: in times of little rain, the stream is shallow and sluggish, 
and exposes a multitude of rocks along its bed; during periods of 
heavy rain it often becomes a veritable torrent, flooding the adjoin- 
ing lowlands, destroying crops, and washing away bridges. It fol- 
lows a direction agreeing in general with the trend of the geological 
formations. Entering the district near the Silver Hill Mine, it 
flows in a southwest direction through both flat lying and hilly 
country, and finds its way past Mat Swamp Ridge, which in some 
places rises rather steeply from the eastern bank. Indeed its banks 
are largely steep and rocky. In its whole course, the stream seeks 
out boundary lines between rock formations of different kinds. 

Abbott's Creek is only slightly smaller than Flat Swamp Creek, 
and is a similar stream. It enters the area about 2 miles west of 
Silver Hill and passes one-half mile east of Fairmont. It follows 
the usual southwest direction until, within a mile of the river, it 
deserts the trend of the slates and flows southeast across this forma- 
tion, entering the Yadkin at a sharp angle at a point near the mouth 
of Flat Swamp Creek. The jointing that is prominently developed 
here or a possible fault plane may be the determining influence in 
controlling the course of the stream. 

Lick Creek and Cabin Creek are somewhat the counterparts of 
Flat Swamp and Abbott's Creeks. They follow more or less parallel 
courses, agreeing with the trend of the schistose formations, though 
having minor variations in the more massive phases. Cabin Creek 
enters the district near Jacksonhill and flows into the Yadkin a mile 
north of Bald Mountain. Lick Creek is nearer and parallel to Flat 
Swamp Ridge. Two tributaries of equal size make up the latter 



78 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

stream ; the one passes just to the east of Kemp Mountain, the other 
flows near its western edge. The two join a short distance south 
of this elevation. 

In addition to the four streams just mentioned, two of which flow 
the length of the area, there are a multitude of small tributaries and 
branches, which include all directions in their various courses. 
These deserve little detailed notice, save that they are controlled 
more by the surface configuration induced by the four major streams 
than by the structural and geological nature of the underlying for- 
mations. Buddie Branch, a tributary flowing south from Silver Hill 
into Abbott's Creek, will serve as an example. This stream cuts at a 
small angle across an area of slate standing on edge. It is believed 
that in this and similar instances the proximity of the larger stream 
has overcome the tendency of the smaller to follow the structure: 
this may be aided by a system of joint planes, or possibly by minor 
faults. One stream in particular seems to owe its direction to fault- 
ing or important jointing. This is Fourmile Branch, a tributary to 
Flat Swamp Creek, which pursues a remarkably straight course 
mostly in massive formations for the 6 miles of its extent. Two 
large diabase dikes coincide with the stream, whose course is, more- 
over, parallel to possible faults indicated on the geological map. 
These features suggest strongly, if they do not prove, that this stream 
follows either fault or joint planes. Most of the smaller streams, 
however, do not show such regularity. 

Summary. — To sum up, the streams of the district are of three 
orders: first, the master stream or that conditioned by a previous 
topography; second, the streams depending upon the structure and 
hardness of the underlying rock; and third, the streams and stream- 
lets which flow into those of the second class, and are controlled by 
their proximity to them, though in part consistent with the structure 
and the geological formation. The drainage, therefore, has been 
developed to its present stage through the application of the three 
sets of conditions outlined above. 

PHYSIOGRAPHIC HISTORY. 

The present surface of the region, when analyzed in its relation 
to the kind and condition of underlying rock, presents certain lines 
of evidence or clues as to its previous condition. From these can be 



• PHYSIOGRAPHY. 79 

deduced the topographic changes which have taken place and the 
order in which they have occurred. 

When the great series of slates, tuffs, breccias, and flows, which 
compose the district, were compressed and thrown into enormous 
folds, a complex surface was formed, the nature of which we can 
only conjecture. This was attacked, perhaps even during its for- 
mation, by the forces of erosion; and denudation was carried to such 
an extent that the region was beveled across hard and soft forma- 
tions alike and reduced to a condition of practically no relief; or 
technically, to a peneplain. Upon this surface, lying near sea level, 
an entirely new system of drainage was inaugurated by a slight ele- 
vation or tilting of the land. This system, of which the Yadkin is 
the remnant, was not controlled by the underlying rocks, because 
these lose their influence near sea level, but probably was condi- 
tioned by the nature of the tilting. At any rate, as evidenced by 
the Yadkin, the main direction of this drainage was in a northwest- 
southeast line and directly across the hard and soft formations. 

The establishment of this line of drainage was followed by a pro- 
gressive elevation of the land, during which the surface was thrown 
into relief and a struggle was carried on : on the part of the drainage, 
to maintain its original direction; on the part of the slowly rising 
land, to divert the drainage from its anomalous course into conformity 
with the structure. That the land was not sufficiently energetic in 
elevating itself to offset the downcutting of the streams is shown by 
the present position of. the Yadkin River, which flows through a nar- 
row gap in Flat Swamp Ridge. The river succeeded in downcutting 
at a rate slightly in excess of the elevation. That the two opposing 
forces were almost matched is suggested by the present course of 
rapids within the gap, which excessive downcutting on the part of the 
river would have prevented. 

During the contest between Flat Swamp Ridge and the Yadkin 
River, or in a broader sense between the rising Piedmont Plateau 
and the master drainage, the chemical and mechanical forces of 
weathering were busy in their attacks upon the region. Streams sub- 
ordinate to the Yadkin were developed which found their easiest 
path in agreement with the structure. These carved out northeast 
trending valleys, separated by ridges, and gave rise to a host of smal- 
ler dependent streams. Thus, as a result of the elevation of the 
land and the downcutting of the streams, the present surface con- 
figuration was developed. 



80 THE CID MINING- DISTRICT OF DAVIDSON COUNTY. 

SURFACE CONFIGURATION OF THE VARIOUS FORMATIONS. 

Many of the rock formations of the district form distinctive kinds 
of surfaces. Certain rocks will predominate in valleys ; others will 
compose the ridges. The different rock types will therefore be enu- 
merated, accompanied by brief statement of their dominant surface 
form. 

Slate: Forms valleys, gentle slopes, well rounded divides. Never 
prominent on uplands and ridges. Massive and mashed phases form 
about same type of surface. 

Acid fine tuff: Occurs as narrow bands in other formations and is 
controlled by their surface forms. Mostly low lying country. 

Acid coarse tuff: Stands up higher than slate. Forms minor 
ridges. Usually intermediate in height between slate and acid vol- 
canic breccia. Forms terrace on west side of Flat Swamp Ridge. 
When schistose, has about same surface configuration as slate. When 
narrow intercalations in other rocks, is controlled by them. 

Acid volcanic breccia: Together with the rhyolite forms the most 
prominent ridges of the region. Called locally "mountain rock." 
Surface always covered with enormous boulders and rounded out- 
crops. Mashed phases form lower surfaces, but the rock is predomi- 
nantly massive. 

Rhyolite: Shares with acid breccia the property of forming the 
highest ridges. Ridges usually narrow, with steep slopes. When 
schistose, differs little from coarse tuff or slate. 

Dacite: Stands up nearly as prominently as rhyolite. Kemp 
Mountain has a more rounded appearance, with gentler slopes, than 
the rhyolite and breccia ridges, such as Flat Swamp Ridge. 

Andesitic tuffs and breccia: Form rather prominent ridges, which 
are not so narrow or steep as the ridges of acid rock. Ridges may 
have little or no elongation. Form elevated, well rounded, plateau- 
like regions as west of Bald Mountain. Massive and slightly schis- 
tose phases act much the same. Badly mashed phases and narrow 
beds conform to topography of adjacent rocks. 

Andesite: When narrow, does not form prominent surface features. 
When associated with basic breccia, as on Three Hat Mountain, 
forms prominent ridges. 

Gabbro dikes: When large, form low, well rounded, mound-like 
ridges. When smaller, have little influence on topography or form 
slight depressions. 

Diabase dikes: Too small to have appreciable topographic effect. 
Largest apt to be slightly depressed. 



CHAPTER V. 

STRUCTURE AND METAMORPHISM. 
INTRODUCTION. 

Previous chapters deal with the nature of the rocks of the district, 
and their relations to one another. In them it has been possible 
to identify and classify the rocks, though they have been profoundly 
changed both chemically and physically since their original consolida- 
tion. It is the purpose of the present chapter to discuss these 
changes — features not inherent in the rocks themselves, but which 
have been imposed, during the vicissitudes the region has undergone, 
by the forces that have operated. Thereby is afforded evidence 
for deducing the nature of the forces and the order in which they 
acted; and thus the sequence of events or geologic history is ar- 
rived at. 

STRUCTURAL FEATURES. 

FOLDING. 

The region has been squeezed into great folds during a period of 
severe compression, the most evident effect of which has been the 
mashing of many of the rocks into schists. The folds may not be 
directly observed, but their presence is inferred from three concur- 
rent lines of evidence. 

1. Bedding planes, which indicate a former horizontal extent often 
depart from this direction, and have a variable dip either to the 
northwest or to the southeast, and at times are even vertical. Were 
these sufficiently well preserved, they alone would indicate the exact 
nature of the folding; but they are much obscured by schistosity and 
weathering, so that only here and there can a measurement be ob- 
tained. Certain generalizations, however, may be made. Bedding 
planes are predominantly horizontal along certain northoast-?onth- 
west lines in massive formations; and tend to be vertical or nearly 
so in the badly mashed belts. 

- 2. The surface outlines of the formations, best seen on the geologic 
map, are indicative of folding. In general, the formations may be 
divided into two classes: first, those which appear upon the sur- 

6 



82 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

face, as long, narrow strips, which gradually pinch out at the ends 
and never end abruptly against other formations; and second, 
those which occur in broad lenses and oval areas, of little or no 
elongation, often ending abruptly against other formations. There 
are of course no hard and fast lines in such a division. Many of 
the narrow bands are flow rocks or tuffs and breccias, which must 
have been deposited in layers or beds of. horizontal extent. Their 
surface outline seems to preclude any other possibility than that 
they are the upturned edges of such beds, which now intersect the 
surface vertically, or nearly so. Broader lenses and oval areas, al- 
though often composed of the same rock as the narrow strips, can 
hardly have the same underground relations. If these, too, represent 
the edges of beds and consequently expose their cross-section, the 
abrupt endings of such formations and the great fatness of many of 
the lenses are difficult features to explain. Besides, the predomi- 
nance of horizontal bedding near such formations is quite incompat- 
ible with such an idea. A satisfactory explanation lies in the con- 
sideration of these areas as occurring on the crests of great folds. 
This position allows of a most irregular surface shape, with abrupt 
endings against other formations, when planation has exposed a 
particular bed to view ; and is moreover in accord with existing bed- 
ding planes. 

3. The relation between schistose and massive formation throws 
further light on the structure. Schistosity is not developed alike 
in all parts of the area; it appears to have had a selective action, 
so that some belts are predominantly massive, whereas others are 
badly mashed. This might be explained by a difference in nature 
of the formations, by virtue of which certain ones were more suscept- 
ible to mashing than others. But such a view leaves unexplained 
why such rocks as the andesitic breccia and acid fine tuff, for instance, 
are so massive in some places, and in others form the most highly 
schistose rocks of the district. It would seem, therefore, that the 
position of a rock was a much more imporant factor in determining 
its degree of mashing than its nature. It follows, accordingly, that, 
although the region as a unit was subjected to compression, some 
portions were so situated as to escape any important effects of such a 
force, whereas others received the full effect of dynamic metamor- 
phism. The crests of folds would afford positions favorable for the 
transmission of a great force, without important molecular adjust- 



STRUCTURE AND METAMOEPHISM. 83 

ments ; the limbs would involve a greater slipping between beds and 
consequently would be susceptible to the greatest degree of mash- 
ing. This assumption best fits the facts observed. 

The three lines of evidence concur in making pretty conclusive 
proof that the region is folded. The exact nature of the folding 
is a more difficult thing to determine. Yet an application of the same 
three principles indicates that the region very probably represents 
in general two anticlines and one syncline, the axes of which ex- 
tend in a northeast direction in agreement with the schistosity. 

The crest of one anticline is supposed to pass to the east of Fair- 
mont and the Silver Hill Mine : along this line the formations show 
upon the surface as broad irregular lenses, which do not pinch out 
at the ends; the bedding, though much obscured, seems predomi- 
nantly horizontal; and the formations are on the whole more mas- 
sive than mashed. The crest of a second anticline probably includes 
Jacksonhill, Denton, and Kemp Mountain: along its axis the bed- 
ding varies little from the horizontal; the formations are not at- 
tenuated, but of round or oval contour; and the rocks are more or 
less massive. Flat Swamp Ridge is considered the trough of the 
syncline between the two anticlines : bedding is not sufficiently de- 
veloped here to be of importance ; but the formations are mostly mas- 
sive and form extremely long and narrow strips, suggestive of the 
upturned edges of beds. Moreover, the most highly schistose rocks 
of the district are not characteristically found along the three lines 
mentioned; but in places between them which correspond to the 
limbs of the folds. The evidence, while not conclusive, is sufficiently 
strong to render this interpretation quite probable. 

Consequent upon the major folding, a series of subordinate 
crumplings and crinklings were of necessity formed; but these 
have been so obscured by weathering and other changes as to baffle 
detection. Their presence is only indicated by an occasional bedding 
plane out of all accord with other measurements in its vicinity. 

It is probable, also, that the major folds are not absolutely hori- 
zontal, but pitch slightly, so that their crests form wavy lines. No 
direct measurements of pitch can be obtained, but inference as to 
its nature may be made from the way in which certain formations 
end abruptly against others, as if dipping beneath them. A further 
evidence is the occasional discordance between trend of bedding and 
of schistosity, indicative of a complexly folded region. 1 

'Van Hise, C. R. Principles of North American Pre-Cambrian geology. 16th Ann. Report, U. S. 
Geol. Survey (1895): 629, 630. 



84 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

In addition to these major and minor directions of folding, whose 
axes form a horizontal plane, the whole region has perhaps been 
slightly bent around a vertical axis. A glimpse at the geologic map 
will disclose the tendency of the formations and the schistosity to 
form an arc-like arangement ; in general, varying from a northeast 
trend near the river to a more northernly direction as the npper 
limits of the map are approached. 

MASHING. 

It has been suggested in the previous section how schistosity, by 
virtue of which a rock tends to break more or less perfectly along 
a certain plane, has been induced upon much of the region by the 
same compression which occasioned folding, and how this has been 
more prominently developed on the limbs of the folds than on the 
crests or in the troughs. A further deduction, however, may be 
made from the nature of the schistosity; and that is the direction 
along which the compressive force acted. The average trend of 
schistosity is JST. 50° E. Theoretically, therefore, the compression 
acted along a line passing K 40° W., as the effects of compression 
are at right angles to the force. 1 This figure must not be taken 
as exact, for other factors would complicate the result; but it is 
approximately correct. 

The average dip of the schistosity is about 10° to 80° to the 
northwest. There are extremely few cleavage planes dipping to 
the southeast; such as do are invariably steep, about 80° to 85°. 
This is significant. It suggests that the folds are not upright ; in 
such a case approximately half of the schistosity should have a dip 
to the southeast. Thus there is evidence for believing that the folds 
are slightly inclined, their axial planes agreeing in a general way 
with the average dip of the schistosity. This view is consistent with 
the arc-like arrangement of the formations, which in itself implies 
a slight overriding of the upper crust and an axial dipping of the 
folds toward the center of the arc. 

The northwest dip of cleavage planes and northwest facing con- 
cavity of the arcs is the opposite of conditions holding in the Ap- 
palachians. This may be due either to some undetermined local 
cause, or to an actual reversal of the relations between land and 
sea obtaining in the Paleozoic; so that in the case of the present 

iSee in this connection: Haug, Emile. Traite de Geologie. Vol. 1(1907): 227. 



STRUCTURE AND METAMORPHTSM. 85 

area, the higher segment or land mass was to the northwest, whereas, 
in the case of the Appalachians, as is generally accepted, the higher 
segment or "hinterland" of Suess was to the southeast. The district 
under consideration, however, is too limited in size to afford wide- 
spread generalizations on this point, unless corroborated in the future 
by other observations in the slate belt. 

A diagram has been made (see Plate XXV), showing the trend 
of all observations upon schistosity. This will be discussed in con- 
nection with joints, which have been likewise plotted. 

jointing. 

Joint planes are distributed throughout the district in all forma- 
tions, but are most abundant in areas of massive rocks. In general, 
the degree of jointing decreases with increased schistosity, the two 
features seeming to be complementary. Where bedding is horizontal, 
jointing is invariably well developed. 

These three features are quite in keeping with the hypothesis of 
folding, and are consequently an added bit of evidence in favor of 
this structure. The jointing is considered to be largely the result of 
the compressive force which threw the region into folds and mashed 
many of the rocks into schists. Those rocks, which were situated 
on the crests or in the troughs of folds, escaped to a large degree 
the effects of mashing; but in transmitting the force were them- 
selves broken into blocks bounded by joint planes. 

The significance of the jointing and its relation to other structural 
features can best be shown graphically. To this end a number of 
diagrams have been prepared. 

In diagram 1 (Plate XIV) the trend and number of all joints 
observed in the district are plotted on rectilinear coordinates. The 
vertical directions or ordinates represent the number of observa- 
tions; the horizontal directions or abscissae indicate the trend of 
each joint plane. Thus at a glance may be seen the number of joints 
trending in any given direction; for instance, 14 joints have a strike 
of X. 20° W., etc. The black curve indicates the jointing in the 
slate; the green curve, the total jointing in the district. The differ- 
ence between the two curves gives, of course, the joints in all other 
formations than the slate. The greater number of observations in 
the case of the slate is due to its greater areal extent. 

From diagram 1 (Plate XIV) the following facts appear: There 



86 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

is no important difference in the jointing in the slate and in the 
other formations; the jointing is grouped in four important sets, in 
their order of importance as follows : 

N. 5° W. to N. 30° W.=25° range. 
N. 65° W. to N. 85° W.=20° range. 
N. 15° E. to N. 35° E. =20° range. 
N. 70° E. to N. 85° E.=15° range. 

In diagram 2 (Plate XIV) are plotted, in the same way and on 
the same scale, the diabase dikes (in red), and the quartz veins (in 
black). From this is seen the regular variation of the dikes from 
N. 50° W. to N. 50° E. ; and the tendency of the quartz veins to be 
grouped between the directions N-S". and N. 45° E. The rather 
regular variation for the curve of the veins, in which the maximum 
directions of trend are spaced 15° apart, is interesting. The exact 
significance of this, however, does not appear. 

In diagram 3 (Plate XIV) the schistosity is represented, on the 
same horizontal scale, but on a vertical scale reduced one-fourth. The 
relation between trend of schistosity and that of jointing is strikingly 
brought out. There are few joints parallel to the schistosity; so 
that the curve of the latter is complementary to the curve of the 
former. The quartz veins are seen to have their greatest develop- 
ment in a position intermediate to that of maximum schistosity and 
maximum jointing. Many of the veins, indeed, cut the schistosity at 
a very small angle. 

To show more visibly the relation between schistosity, jointing, 
and the direction of the compressive force, the previous diagrams 
(Plate XIV) are in a measure combined in one diagram (Plate XV). 
In this the various features are plotted on a circle, whose circum- 
ference represents the different points of the compass. The curve 
for total jointing in diagram 1 is transferred to the circle and plotted 
on polar coordinates, so that by reference to it the relative number 
of joints with any given trend may be ascertained. This brings 
out four maximum lines of jointing represented by the four purple 
lines. The four sets of important joint directions appear by con- 
structing segments to contain the maximum areas included by the 
joint curve. These of course are the same as those obtained in 
diagram 1 (Plate XIV) ; and each is bisected by the maximum line 
of jointing in purple. The directions of greatest schistosity are 
taken from diagram 3 and plotted on the circle in red. The heavy 
black line represents the average direction along which the compres- 



N. C- GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XIV. 




Diagram 1, showing direction and abundance of jointing, black curve = jointing in slate, dotted 
jointing in all formations including slate. 



? " E. 

CURVE = 




Diagram 2, showing direction and abundance of quartz veins and diabase dikes, dotted curve = diabase 

dikes and black curve = quartz veins. 



^ *° 



i : \ 

>' , ' \ 

. L! , 1 ^ 

i ' ' i 

^ — L — I— I — ^i 

/ . , V ' ■ ; ; ■ 

/ ' ' ' [ I ' '. ' \ 



"bon; A/#str AtJe . 



<VJo£ S+4J-E 



D/cyra/7? 3 s-J>ow;/7j c/;rec/ '/ ao & &<i>cs/7 <^&s?c e of' -5 c/p/jfo s/7y . 



Diagrams showing relations of joints, veins, dikes and schistosity. ordinates = abundance (number of 
observations) and abscissae = trend. 



STRUCTURE AND METAMORPHISM. 87 

sive force acted; it is given its theoretical value — i. e., at 90° to 
the maximum schistosity. 

Certain features are brought out rather clearly by this diagram. 
Also certain details invite some speculation. The four major joint 
sets are grouped two in the northwest quadrant and two in the north- 
east quadrant. Those in the northwest quadrant are of the greater 
importance; they are separated from each other by an angle of 35°, 
which includes the direction of compression. This double set seems 
to be largely the result of the compressive force, inasmuch as the 
maximum line of each (in purple) is inclined 20° and 35° to the 
line of compression; and because jointing from compression is de- 
veloped in the 'lines of shear, which are inclined 45° or less to the 
force producing them. The double set of joints in the northeast 
quadrant may be explained in several ways. They cut the schistosity 
at small angles and the line of compression at large angles. They 
may be due to the same compression that induced schistosity ; if so, 
this necessitates a degree of shortening involved in compressing the 
diamond in the northwest quadrant into the shape of the diamond 
in the northeast quadrant. They may be the result of a secondary 
force from the northeast or southwest, either an independent one or 
a component of the major compression. Perhaps a combination of 
all these acted. There is no evidence for believing any important 
jointing on the crests of folds to be due to tension : joints from such 
a cause would be parallel to the schistosity developed on the limbs 
of the folds. 1 

It must be understood that all jointing in the region is not com' 
sidered the result of a single period of compression and folding. 
There is doubtless jointing from other subsequent earth movements. 
It does seem probable, however, that the most prominent jointing is 
consequent upon folding. 

FAULTING. 

While there is at no place conclusive evidence of faulting on an 
important scale, a number of possible faults have been indicated on 
the geologic map. These can not be verified by field observations ; 
but their presence is suggested by the abrupt ending of certain forma- 
tions, as if cut off by dislocations, and in cross-section by the failure 
of bands to be repeated on corresponding parts of folds. The smaller 

Geol V Sur?ey e (1895)!'669! rinCipleS ° f N ° rth American Pre-Cambrian geology. 16th Ann. Rept., U. S. 



88 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

faults have a general parallelism to one another, and to Four- 
mile Branch, which pursues a remarkably straight course for 6 miles 
and agrees in direction with two large diabase dikes. They are also 
roughly parallel to the strike of a profound fault a few miles to the 
west, which Laney 1 has shown separates the slate series from a large 
area of igneous rocks. 

A large overthrust fault has been indicated as extending along the 
eastern border of Flat Swamp Ridge in a northeast direction and 
becoming northernly in trend near the upper borders of the map. 
Its presence seems necessitated by the way in which broad belts of 
rock appearing on the western slope of Flat Swamp Ridge are not 
repeated on its eastern declivity, as would be expected on the two 
limbs of a syncline. Either, then beds 1-2 mile or so in thickness 
must pinch out along their dip in the course of a mile or they must 
be abruptly cut off by a fault. The latter conception is the simpler. 
A glance at the structure-section sheet (Plate IV) will make this 
idea clear. 

The faulting is probably the result of the same compressive force, 
which induced folding, schistosity, and jointing. It is possible, how- 
ever, that the coming to place of great granitic batholiths a few miles 
to the west may have exerted sufficient compression to occasion over- 
thrust faulting on a large scale. Certainly this event very likely 
produced minor faulting and shattering. 

INTERPRETATIONS OF STRUCTURE. 
MOST PROBABLE INTERPRETATION. 

The reasons have already been presented for believing the region 
to be made up of a series of inclined folds, whose axial planes dip 
steeply to the northwest. This interpretation is represented on the 
structure-section sheet (Plate IV), which shows cross-sections at 
several points across the district. By means of these, the under- 
ground relations of the rocks which appear upon the surface are indi- 
cated. In a general way, the cross-sections are what might be ex- 
pected to be exposed, were great trenches cut across the region. 

While the major features of the structure seem established with 
some probability, there are minor features upon which no direct evi- 
dence can be obtained ; yet which must be expressed upon the struc- 
ture-section sheet in a definite manner. It must be remembered, 

iLaney, F. B. The Gold Hill mining district of North Carolina. A Thesis. Yale University 
1908): 112. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XV. 







The h/acfc 
c c/r re re/yre-5 e/?/s 
tf>e rg/aJ/jse ni/m tier ' 
f-ja/nts. 

Diagram showing relations between compressive force, schistosity and directions of maximum jointing, 
the maximum line of jointing for each set is the radial line. 



STRUCTURE AND METAMORPHISM. 89 

therefore, that a diagrammatic representation is ideal and from 
the nature of the case expresses only in a summarized manner the 
conditions which exist in nature and omits an infinity of detail, 
whose inclusion would only serve to confuse. 

In the cross-sections given, no minor crumplings are indicated on 
the major folds. Such undoubtedly exist, but they are omitted 
both for the sake of simplicity and because their nature is not known. 
The thickness of those beds, whose cross-section in no place is ex- 
posed to the surface, is entirely hypothetical: the thickness given 
in each case is considered a probable one, from which, however, the 
true thickness may depart rather widely. If it be attempted to 
trace out each formation as it is successively brought to the surface 
by the folding, it will be found that the beds do not always match on 
the opposite limbs of the folds. This is understood, if it be ac- 
cepted, that the original horizontal extent of the formations con 
sisted of a complicated inter fingering of beds and lenses, and was 
not a succession of regular beds of the same thickness throughout 
their lengths. In such a case it would not be expected that folding 
would necessarily repeat similar beds on corresponding parts of 
folds. Along Flat Swamp Eidge, however, this explanation seems 
inadequate, inasmuch as beds of great thickness must pinch out with 
extreme rapidity in order to avoid repetition. In order to obviate 
this difficulty an overthrust fault has been introduced as a simpler 
explanation. The arc-like surface trace of this supposed fault plane 
renders it probably an overthrust consequent upon the northwest 
compressive force of folding. The fault plane may itself be folded, 
depending upon whether the slip occurred at the beginning or near 
the end of the period in folding. In the cross-sections the latter con- 
ception is prefered, because simpler. 

The manner in which the major folds pitch is inferred from the 
abrupt endings of many formations along the crests of the folds, pre- 
cluding a horizontal entension of this line. 

ALTERNATE HYPOTHESES. 

Although the interpretation of structure given appears to best fit 
the facts ; some alternate hypotheses, especially in regard to the sub- 
ordinate features, may be mentioned. 

As suggested in previous paragraphs, the entire structure may be 
explained without the use of faults. This necessitates the pinching 
out of beds of s^reat thickness within very short distances. 



90 THE CID MINING DISTKICT OF DAVIDSON COUNTY. 

A portion of the rocks may have been brought into the region by 
an overthrust fault; and these subsequently interfolded with the 
regional rocks. 

The region might possibly represent a series of isoclinal folds, 
with parallel limbs. 

That the region may not be folded and represents a very thick de- 
posit, which has been tilted and whose edge is now cut across by the 
plane of erosion, seems hardly a possibility. 

METAMORPHIC FEATURES. 

TEXTUEAL CHANGES INVOLVED IN MASHING. 

The textural changes imposed upon the rocks by compression have 
been discussed in various parts of the chapters descriptive of the 
rocks. It was there seen how nearly every rock type varies from a 
massive condition to a schistose state, having had induced upon it in 
some parts of its areal extent a certain degree of cleavage or schis- 
tosity, by virtue of which the rock breaks rather easily along definite 
planes. Sericite schists are the products of the extreme mashing of 
the acid series of rocks ; greenstone schists have in the same way been 
derived from the basic series of rocks. 

MINERALOGIC CHANGES INVOLVED IN MASHING. 

From a microscopic study of massive and mashed phases of each 
rock type, certain minerals are seen to increase in abundance with 
the degree of mashing. These have apparently been developed, 
therefore, as a result of compression. Descriptions of such second- 
ary minerals formed through dynamic metamorphism have been 
given in various parts of chapter III on Petrology, but it may be 
well to summarize these statements in this place. The following 
minerals appear to be largely or partly the result of dynamic meta- 
morphism: sericite, biotite, chlorite, actinolite, epidote, and clino- 
zoisite. Sericite is the most abundant secondary mineral in the acid 
series of rocks, so that the end product of mashing is a sericite schist. 
In the acid rocks are also found smaller amounts of biotite, chlorite, 
epidote and clinozoisite. These four minerals, with actinolite, are 
.specially characteristic, however, of the basic series. Most of them 
are abundantly present in the greenstone schists, which result from 
the extreme mashing of any of the basic rocks. Chlorite is a close 



STRUCTURE AND METAMORPHISM. 91 

accompaniment of biotite, and the biotite in many cases passes into it. 
Likewise the epidote and clinozoisite always occur associated, and 
the epidote alters to clinozoisite. The last two, and perhaps actinolite 
also, are probably only in part due to dynamic metamorphism. 

SIEICIFICATION. 

An important feature of the district is the highly silicified nature 
of many formations. This is indicative of a period during which 
large amounts of silica were brought in and deposited. The quartz 
veins now exposed probably represent the trunk channels along which 
silica-bearing waters moved. The mineralization and segregation 
of ores is also considered a result of the same general period. 

DETAILED DISCUSSION OF GEOLOGIC HISTORY. 

IGNEOUS ACTIVITY. 

The geologic history of the Cid Mining District may be consid- 
ered as having its beginning during a period of volcanic activity. 
This must have extended through a very long time — hundreds of 
thousands or even millions of years — during which there were in- 
numerable alternations between quiet upwellings of lava, forming sur- 
face flows; explosive activity on an enormous scale, piling up to a 
great thickness deposits of tuffs and breccias; and periods of com- 
parative quiescence, accompanied by a certain amount of weathering 
and erosion and the deposition of the slates. Between successive out- 
breaks, the magma probably underwent some degree of differentia- 
tion so as to give rise to more acid rocks at one time, and more basic 
rocks at others. It seems pretty probable that there were frequent 
swings between two not very diverse extremes, and that at no time 
did the products depart far from the general type, which is a rather 
acid magma rich in soda. Perhaps each important outbreak poured 
forth rhyolitic, intermediate, and andesitic materials. 

It would be impossible to picture the details of this volcanic ac- 
tivity. It is suggested, however, that the outbreaks were largely 
fissure eruptions, breaking up through the series of already formed 
horizontal rocks at frequent points in the entire volcanic region. It 
must not be thought that any one volcanic cone, comparable to a mod- 
ern volcano, gave rise to such widespread volcanic phenomena. 1 

iSee Hague, Arnold. Early Tertiary volcanoes of the Absaroka Range. Pres. Add., Geol. Soc. 
Wash. (1898): 1-25. 



92 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 



SEDIMENTATION. 

All of the slate and much of the fine tuff give evidence in bed- 
ding planes of deposition by water. The coarse tuffs and breccias 
may be air-laid or water-laid, or both. The flows may have taken 
place upon the surface of the land or under water. Possibly the 
entire series represents an off-shore deposit, with submarine volcanic 
activity alone or accompanied by outbreaks upon the shore. The 
region may also represent a river flood-plain deposit. Nothing re- 
mains to decide definitely between the two hypotheses. 

It is believed from chemical evidence that the slate material was 
transported from no great distance. Hence a probable view is to 
consider the volcano-sedimentary series a basin deposit, the material 
for which was derived from beneath an area of limited extent, and 
the thickness of which was limited only by the depth of the "magma 
reservoir" and the amount of material extruded ; so that by isostatic 
sinking of the crust block capped by a layer of volcanic and sedi- 
mentary rocks, as more material was forced up through it and de- 
posited upon its top, a series of great thickness could have been 
formed, without drawing materially upon the surrounding country 
for sediments and conversely without bestowing evidences of its 
nature upon regions not within its own confines. 

CONSOLIDATION. 

However laid down, the tuffaceous and sedimentary rocks must 
have undergone cementation or consolidation before they were capable 
of being thrown into folds. This process doubtless accompanied the 
formation of the deposits, so that within a short period of geologic 
time after the cessation of volcanic activity, the series had been 
transformed into strata of hard rock. The rapidity with which 
this may be accomplished is seen by comparison with the ashes 
ejected by modern volcanoes, which are at times known to "set" or 
harden within a few days of their deposition. 

FOLDING AND THE DEVELOPMENT OF SCHISTOSITY, JOINTING, AND 
PROBABLE FAULTING. 

No evidence is afforded for estimating the length of time which 
intervened between the formation of the rock series and its folding. 
It may be that the compression put an end to the constructive epoch : 



STRUCTURE AND METAMORPIIISM. 93 

or it may equally be that this force was long deferred. At any rate, 
the region of horizontal beds and lenses was powerfully compressed 
by a force acting in a northwest-southeast line ; the effects of which 
were folding, mashing, jointing, and faulting. 

These four features have been sufficiently discussed in previous 
parts of this chapter. 

INTRODUCTION OF GABBRO DIKES. 

Following, after an unknown interval, the mashing or development 
of schistosity, a great number of gabbro dikes were insinuated into 
the region, following cleavage planes as easy lines of entrance. 
These are undoubtedly later than the folding, because they are con- 
trolled in direction by the schistosity and are themselves unmasbed. 
The dikes represent either the outliers of an independent gabbro 
batholith or the differentiated offshoots from a large "magmatic 
reservoir" of a more acid nature. 

A few miles to the west of the Cid district, and forming the west- 
ern boundary of the entire slate belt, occur areas of granitic, dioritic, 
and other igneous rocks, which cover many hundred square miles. 
These are undoubtedly intrusive batholiths into the slate series. 
They do not, however, represent a single intrusive mass, which has 
become differentiated to the extent of forming areas of granite, 
diorite, etc. In the Gold Hill region Laney 1 has shown that granite 
is intrusive into diorite; also that dikes of gabbro cut the diorite 
but not the granite. Thus there seems to have been a period, fol- 
lowing the folding of the slates, when great masses of igneous rocks 
were intruded into the region. While there were independent in- 
trusions, all were probably the result of a single period of activity 
and all perhaps originated from the same "mngmatic reservoir." 

In view of these considerations, and because gabbro is found in the 
Gold Hill district intermediate in age between great intrusions of 
diorite and granite, the gabbro dikes of the Cid district are con- 
sidered to have originated during a period of intrusive igneous ac- 
tivity and to be related to the igneous rocks a short distance to 
the west. 

PASSAGE OF HEATED SOLUTIONS. 

Previous to the approach of the great igneous masses, heralded by 
the introduction of the gabbro dikes, there is no evidence of pro- 

^aney, F. B. The Gold Hill mining district of North Carolina. A Thesis. Yale University 
(1908): 121; and N. C. Geol. and Economic Survey, Bull. 21, 1910. 



94 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

cesses sufficient to account for widespread mineralization and sili- 
cification ; unless, indeed, the original rocks be considered sufficiently 
rich in silica and metallic elements to permit of important concen- 
tration by ground-water circulation. Yet many formations have 
been enriched "en masse" by silica, while none show signs of deple- 
tion of this compound. Moreover, numerous quartz veins evidence 
a further amount in excess of what the rocks themselves seem com- 
petent to contribute. On the other hand, vapors and waters, with 
their burden of metallic elements, excluded by the great igneous 
masses which probably undermined the region, and certainly ap- 
proached it, seem quite capable of having occasioned widespread 
silicification and mineralization ; forming quartz veins along lines of 
major circulation and enriching places favorable for deposition by 
the formation of ores. 

This subject is considered in greater detail in Chapter VI under 
the genesis of the ores. 

OPERATION OF A SECONDARY FORCE, INDUCING MINOR JOINTING. 

There' is some evidence that, following the deposition of the ores, 
there operated a force which occasioned minor jointing throughout 
the region. The evidence is twofold : first, the gabbro is cut by well- 
defined joint planes, which are of such a nature as could hardly be 
due to contraction through cooling; and second, small offsets in the 
veins are- occasionally met with in the mines. If such a force 
operated, it was a comparatively unimportant event in the history 
of the region. 

It is possible that there was jointing as the results of several 
earth movements subsequent to the folding. 

INTRODUCTION OF DIABASE DIKES. 

The first event of known age is the introduction of diabase dikes. 
These were introduced in Triassic time ; for the same rock is found 
elsewhere cutting both slate and Triassic sandstone. The length of 
the interval between the period of ore deposition and the coming to 
place of the diabase is not known, but is undoubtedly large. The 
diabase cuts the gabbro presumably along joint planes ; in the other 
formations it also appears to have been introduced along joint 
directions. 

WEATHERING AND EROSION. 

Although operative to a greater or less degree since the region was 
first elevated by folding, the forces of weathering and erosion have 



STRUCTURE AND METAMOEPH1SM. 95 

been especially active from the introduction of the diabase to the 
present. This period, then, is dominantly one of plantation and 
rock decay; to such an extent, indeed, that the entire region has 
been reduced once to an approximate base-level, and although re- 
juvenated by uplift, is again approaching that state. The result of 
this very last chapter in the geologic history has been to blur over 
and destroy the records of the previous chapters ; yet enough remains 
to construct a sequence of events, which represents in fair measure 
the geologic development of a unique region. 

SUMMARY OF GEOLOGIC HISTORY. 

1. Building up of the volcano-sedimentary series. Alter- 
nations of volcanic activity and periods of quiescence. 
Pre-Cambrian (?). 2. Consolidation of the series. 

3. Operation of a compressive force, throwing the whole 

formation into folds, and inducing schistosity, joint- 
ing, and probable faulting. 

4. Approach of a mass of igneous rock, announced by the 

insinuation of gabbro dikes into the region. 
Paleozoic (?). 5. Passage of solutions, depositing iron ores and silica, 

and forming quartz veins and mineralized zones. 
6. Possible second period of earth movements, inducing 

some jointing. 
Triassic. 7. Introduction of diabase dikes. 

Post-Triassic. 8. Period of weathering and erosion. 

THICKNESS AND AGE OF THE SLATE SERIES. 

Thickness. — Nothing definite can be said as to the thickness of 
the slate series. From the cross-sections, however, it appears prob- 
able that the series is about from 2 to 4 miles thick. This estimate 
is given by no means as a final figure, but with the hope that future 
work in the same province may turn it into something more definite, 
corroborative or otherwise. 

Age. — Again, nothing final can be said about the age of the slate 
series. It is generally considered as Pre-Cambrian. Volcanic rocks 
of a somewhat similar nature in the South Mountain region of Penn- 
sylvania occur beneath Cambrian sandstone. 1 As there is no evi- 
dence to the contrary, the present series is provisionally correlated 
with the Pre-Cambrian. 

iWilliams, George H. The volcanic rocks of South Mountain in Pennsylvania and Maryland 
Am. Jour. Sci., v. 44 (1892): 493-494. 



CHAPTER VI. 

ORES AND MINES OE THE DISTRICT. 
HISTORICAL. 

The history of the mining development in Davidson County is 
largely a record of attempts to successfully treat the ores. In the 
earliest history of each mine, the surface ores, which required but 
little skill for their winning, were mined by individuals; but the 
finding of complex sulphides at depth in each case necessitated the 
formation of a company and installation of machinery to success- 
fully meet the changed conditions. 

It cannot be ascertained when the earliest prospecting was done 
in this locality, but it is probable that during the first 25 years of 
the 19th century some gold was obtained. In 1824 Olmsted 1 men- 
tioned Davidson County as a part of the gold country. About 1830 
there was some prospecting carried on near the present Peters mine. 
In 1838 the Silver Hill mine was discovered and soon this mine was 
in active operation, although much difficulty was encountered in the 
attempts to treat the complex mixture of galena and sphalerite, 
which was met with. Between 1838 and 18G2 active mining was 
rather extensively carried on in many parts of the county, and 
attention was directed not only to gold, but to silver, lead, zinc, and 
to a less extent to copper. During this period, the district, and espe- 
cially the Silver Hill Mine, attained some prominence as a mining 
center. The Civil War of 1861-G5 occasioned a cessation of activity, 
but work was resumed at several of the mines shortly after. Be- 
tween 1875 and 1885 there was a second period of activity in pro- 
duction and exploitation of new properties ; but from the latter date 
to 1909 the production has been small. 

PRODUCTION. 

It is an impossibility to estimate with accuracy the total produc- 
tion of any mine or of the district as a whole. Between 1882 and 
190G, according to the reports of the Director of the Mint, the 
production of Davidson County amounted to about $110,000, mostly 
gold. Previous to 1SS0, the reports of the Director of the Mint 

iQlmsted, Denison. Report on the geology of North Carolina. Raleigh (1825-27) : Z8. 



ORES AND MINES OE THE DISTRICT. 97 

were included in the annual reports of the Secretary" of the Treasury, 
and gave only the production of the State as a whole. The total 
production of gold and silver for North Carolina up to 1894 was 
estimated by Hanna 1 to be about $24,000,000, of which nearly 
$12,000,000 had appeared on the United States records. Excepting 
the Gold Hill Mine, the Silver Hill Mine is the most extensively 
worked and deepest mine in the State. It is very probable, there- 
fore, that the production of Davidson County from the beginning 
amounts to several million dollars, the greater portion of which rep- 
resents the output of the Silver Hill Mine. • ■ 

Cost of production.— Little definite information can be given as 
to the cost of mining. Labor and fuel are low in price, and work 
can be carried on during the entire year. The water in the mines 
is not excessive. In the Emmons Mine, "drifts cost from $5 to $6 
per foot when driven by hand on contract, the company furnishing 
powder and tools, and $2.50 per foot when driven by machines, 
when the company furnishes air and tools only, contractors furnish- 
ing power, etc. Winzes cost $5 per foot under the same conditions." 2 

PRESENT STATE AND IMPORTANCE OE THE DISTRICT. 

While none of the mines are being worked in 1909, the district 
has not been abandoned. Each of the mining properties is looked 
after by a superintendent, who lives upon the grounds, and the 
equipment of at least two of the mines, the Emmons and Peters is 
in first-class condition, so that work could be started on short notice 
' with little or no initial outlay. The properties are owned by north- 
ern capital, chiefly New York and Baltimore companies, one of 
which has had a representative in the county for the past few years. 
The Silver Hill Mine was sold in 1908, and the Emmons, Peters, 
and Conrad Hill mines are reported to soon begin work. 

_ It seems probable, therefore, that with the return of stable finan- 
cial conditions, some work will again be carried on in the region. 

DESCEIPTIOtf OF THE MI1VES A1VD PEOSPECTS. 

Seven mines and numerous smaller workings, some of which are 
locally c alled mines, represent the mining development in the Cid 

3 (1896) : Ze i7 H: B * °" ^ ^^'^ G " B " G ° ld deposits of N ^ h Carolina. N. C. Geol. Survey, Bull . 
Induft^in^trth cifolfna io^m^?^ ^^ *" g0ld "^ * N ° rth Car ° lina - (In Mineral 



98 THE CID MINING DISTRICT OE DAVIDSON COUNTY. 

district. These are pretty well confined to the northwest and north- 
east borders of the area mapped; though prospecting on a small 
scale has been carried on in all parts of the district. The largest 
and best known mine is the Silver Hill. Less well known are the 
Conrad Hill, Emmons, Silver Valley, Peters, Cid, and Ward mines. 
The location of these mines is shown on the map. (Plate IV.) 

In 1908, when the field work for this report was carried on, none 
of the mines were in operation. The following descriptions are 
consequently in much less detail than if the underground workings 
had been accessible. The descriptions are based upon surface obser- ' 
vations ; laboratory studies of the best specimens of ore that could be 
obtained from the dumps ; accounts given by reliable men, conver- 
sant with the past development of the mines, many of whom had 
direct supervision of the work; and compilations from all available 
articles descriptive of the mines. The endeavor has been to collect 
data from all possible sources, to select only that which appeared 
authentic, and to combine the whole into an account which will 
represent all that is now known of the mines. 

TYPES OF DEPOSITS. 

The mines and prospects of the district for convenience of descrip- 
tion may be divided into three classes or types of deposits. These 
are designated as follows : 

1. Silver Hill type, in which the ores consist of a complex mix- 
ture of galena and sphalerite, together with pyrite and chalcopyrite, 
the whole carrying silver and gold, in a highly altered country rock 
with little or no quartzose gangue. 

2. The Conrad Hill type, in which the ores consist of auriferous 
pyrite and chalcopyrite in a gangue of quartz, hematite, and siderite. 

3. The Emmons type, in which the ores consist of auriferous 
pyrite and chalcopyrite in a quartzose gangue, or as narrow string- 
ers in the schists with little or no gangue. This type corresponds to 
the Gold Hill type of deposit, described by Laney. 1 

THE SILVER HILL TYPE. 

The Silver Hill Mine. 
Location,— The Silver Hill Mine is situated about 10 miles south- 
east of Lexington and about 4£ miles northeast of Fairmont, near 

~~ iLaney^F. B. The Gold Hill mining district. N. C. Geological and Economic Survey, Bull. 21 , 
p. 83, 1910. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XVI. 




ORES AND MINES OF THE DISTRICT. 99 

the source of Buddie Branch. It occupies the top of a low, well- 
rounded hill, which rises gently from a country of subdued relief. 

History. — This mine, for a long while known as the Washington 
silver mine, and at one time in its earliest history called King's 
mine, was discovered, according to the most authentic accounts, in 
1838. In the spring of that year, "the owner (Byerly) of a small 
tract was led to examine a spot at the top of a hill * * * in 
the hope of finding gold. He found the carbonate of lead and then 
sold his possessions. Mr. Roswell King, who became the purchaser, 
sunk a shaft and fell in with the ores of the other metals, silver, 
copper, zinc, during the summer of the same year, and in the follow- 
ing winter the Washington Mining Company was incorporated." 1 
The surface ores, chiefly lead carbonate with disseminated plates of 
native silver, were easily reduced and yielded handsome returns. 
This was of short duration. Sulphides were soon reached and pre- 
sented great difficulties of extraction. Then began a long period of 
experimentation with the view of successfully separating the pre- 
cious metals from their intimate associates, galena and sphalerite; 
during which time method after method was adopted, only to be sub- 
sequently abandoned, often unfortunately after the installation of 
an extensive and costly plant. 

In the first attempts to separate the metals, only silver and gold 
were saved. Then it was thought that the lead also might be saved 
by the elimination of zinc by volatilization. A difficulty arose in 
the presence of so much zinc, the vapors of which carried off me- 
chanically some of the lead, silver, and gold, which was lost. Later, 
in about 1850, a method was in use for separating the zinc by oxi- 
dation. This process is rather completely described in the Mining 
Magazine for 1853, 2 and is something as follows: The ore is broken 
into coarse fragments and roasted in heaps in the open air, by means 
of wood or wood charcoal. The zinc is thus converted to the oxide, 
which is washed away by water at the stamp mill, while the mass is 
crushed to a fine powder. A portion not completely oxidized is re- 
turned to the roasting piles. The residue, free from zinc, is brought 
to the smelting furnace, called a "high furnace," and there smelted 
with fluxes by charcoal. About one ton of lead is obtained in 12 
hours. The lead is transferred to a refining furnace and concen- 
trated. The rich lead is then taken out and refined in cupels. 

iMitchell, Elisha. Elements of geology; with an outline of the geology of North Carolina. 1842 
2 Gold and silver produced by the mines of America from 1492-1848. Min. Mag., Ser. I, v. 1 (1853): 
365-373. 



100 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

This was evidently found unsuitable, for in 1856 a modification 
was described 1 which depended "upon a mechanical separation of 
the zinc from the silver, prior to its introduction into the smelting 
furnace. This is effected by Bradford's Separators, which, after 
the pulverization of the sulphurets, is detached from the galena by a 
simple shaking movement of a plate of copper, aided by water, over 
which the metals are passing." 

The mine was worked almost continuously by a Philadelphia 
company until 1852, when the workings were allowed to fill with 
water. By this time the deepest shaft had been sunk 15 feet below 
the 200-foot level. In 1844 very rich silver ores and beautiful 
arborescent and dendritic masses of the native metal were obtained 
from between the 60- and 100-foot levels. The production in 1844 
is stated to have been $24,009.01 in silver and $7,253.69 in gold. 
The mine was again in operation in 1854 and work was continued 
until 1861. A portion of the time between 1861 and 1864 the mine 
was operated by the Confederate Government for lead alone. As 
much zinc as possible was separated by concentration at the mine, 
and the ore was shipped to Petersburg, Virginia, where it was 
smelted and the lead used for bullets. Succeeding the Civil War the 
mine was probably at no time long idle until 1882, since when little 
work has been done. 

In 1872 the deepest shaft had reached the depth of 650 feet. 
At this time the ore was separated by buddies after crushing, and 
the buddled ore roasted and shipped to New York for the manufac- 
ture of so-called Bartlett's white lead. 2 For this purpose much of 
the discarded ore upon the dumps was also utilized. It is probable 
that the buddies had been more or less in use during the previous 
20 years. This method is reported as probably the most success- 
ful which has been used. In 1878 a large body of carbonate ore 
was discovered and a part shipped during the two following years. 
The mine was quite active during this period, the efforts being con- 
fined largely above the 250-foot level. But with the working out of 
the oxidized ores, difficulties were again encountered in treating the 
complex mixture of sulphides. This, together with some litigation 
over the title, caused a cessation of work, and in 1882 the workings 
were allowed to fill with water. 



'Emmons, Ebenezer. Geological report of the midland counties of North Carolina. Raleigh 
56): 

-61. 



2 Genth, F. A. On the mineral resources of North Carolina. Frank. Inst. Jour., v. 63 (1872): 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XVII. 




Cross-section of north, saw-mill and inclined shafts of silver hill mine. 



ORES AND MINES OF THE DISTRICT. 101 

In 1898 the mine was unwatered, the incline shaft was enlarged 
and re-timbered fully to the 250-foot level and repaired to the bot- 
tom. Work was carried on chiefly below the 200-foot level until 
1900 by the West Prussian Mining Company and some shipments 
of argentiferous galena and blende were made. In widening the 
shaft above the 200-foot level considerable native silver was found. 
Again the inability to successfully concentrate the ores seems to have 
put an end to the working. A careful survey was made of the under- 
ground workings by Mr. E. Hopkins, the engineer in charge, and the 
results of his survey are reproduced in Plates XVI, XVII, and 
XVIII. 

In August, 1908, the property was reported to have been pur- 
chased by a Xew York company. 

Surface features. — The country rock is predominantly a sericite 
schist, striking about X. 35° E., and dipping steeply to the north- 
west. The two principal veins, known as the "East" and the 
"West," are parallel and 28 feet apart on the surface, though their 
outcrops can not now be traced. The schists in the vicinity of the 
mine are brilliantly colored upon weathered surface, indicative of 
a mineralized zone. An outcrop of andesitic breccia is found within 
a few hundred feet of the main shaft, and belts of the same rock 
occur a mile to the south and to the southeast. The sericite schists 
represent the mashed phases of acid tuffs. Upon the dumps are 
found many specimens showing clearly their fragmental nature. 

Underground development. — The mine has been developed chiefly 
by an inclined shaft in the east vein, which follows the vein for 
about 725 feet to a vertical depth of 570 feet. A vertical shaft, 
known as the Sawmill, Engine, or Whim shaft, connects with the 
inclined shaft at the 160-foot level; and another, known as the North 
shaft, connects at the 250-foot level. Both veins have been worked 
from these shafts by means of connecting cross-cuts. Down to 310 
feet the levels in the east vein were driven each 50 feet on the in- 
cline and extended both northeast and southwest; below 310 feet, 
50 to 75 feet to the north only, since the shoot of ore appeared to be 
pitching to the northeast. The stopes extended: 25 to 50 feet from 
the shaft along the levels, both veins being worked alike. 

The development up to 1898 and the amount of ore stoped is 
shown in Plates XVI, XVII, XVIII. 

"The mine has been more or less prospected for about 700 feet of 



ORES AND MINES OE THE DISTRICT. 101 

In 1898 the mine was unwatered, the incline shaft was enlarged 
and re-timbered fully to the 250-foot level and repaired to the bot- 
tom. Work was carried on chiefly below the 200-foot level until 
1900 by the West Prussian Mining Company and some shipments 
of argentiferous galena arid blende were made. In widening the 
shaft above the 200-foot level considerable native silver was found. 
Again the inability to successfully concentrate the ores seems to have 
put an end to the working. A careful survey was made of the under- 
ground workings by Mr. E. Hopkins, the engineer in charge, and the 
results of his survey are reproduced in Plates XVI, XVII, and 
XVIII. 

In August, 1908, the property was reported to have been pur- 
chased by a Xew York company. 

Surface features. — The country rock is predominantly a sericite 
schist, striking about K". 35° E., and dipping steeply to the north- 
west. The two principal veins, known as the "East" and the 
"West," are parallel and 28 feet apart on the surface, though their 
outcrops can not now be traced. The schists in the vicinity of the 
mine are brilliantly colored upon weathered surface, indicative of 
a mineralized zone. An outcrop of andesitic breccia is found within 
a few hundred feet of the main shaft, and belts of the same rock 
occur a mile to the south and to the southeast. The sericite schists 
represent the mashed phases of acid tuffs. Upon the dumps are 
found many specimens showing clearly their fragmental nature. 

Underground development. — The mine has been developed chiefly 
by an inclined shaft in the east vein, which follows the vein for 
about 725 feet to a vertical depth of 570 feet. A vertical shaft, 
known as the Sawmill, Engine, or Whim shaft, connects with the 
inclined shaft at the 160-foot level; and another, known as the North 
shaft, connects at the 250-foot level. Both veins have been worked 
from these shafts by means of connecting cross-cuts. Down to 310 
feet the levels in the east vein were driven each 50 feet on the in- 
cline and extended both northeast and southwest; below 310 feet, 
50 to 75 feet to the north only, since the shoot of ore appeared to be 
pitching to the northeast. The stopes extendeoT 25 to 50 feet from 
the shaft along the levels, both veins being worked alike. 

The development up to 1898 and the amount of ore stoped is 
shown in Plates XVI, XVII, XVIII. 

"The mine has been more or less prospected for about 700 feet of 



102 THE CID MINING DISTRICT OF DAVIDSON" COUNTY. 

its entire length, but the vein formation extends a much greater dis- 
tance. * * * Two small veins are found from 100 to 175 feet 
in depth ; the Little East vein, a few feet east of the main East vein, 
and nearly parallel to it ; and the Little West vein, some 50 feet 
west of the main vein, and inclining toward it. Small outlying len- 
ticles were encountered occasionally in driving into the 'country/ 
and the main vein was occasionally divided by 'horses' of schist. 

"The veins come together at the 60-foot level just to the south- 
west of the Engine shaft, where the West vein was richer in silver. 
At the depth of about 400 feet * * * the two veins united 
again. * * . * At the 60-foot level, and down to the 100-foot 
level of the West vein, there also occurred a good body of manganese 
ore, and associated with it most of the cabinet specimens for which 
this mine was noted. * * * The West vein also expands con- 
siderably between 60 and 100 feet; but in the expanded parts it was 
regularly defined, and often had 'vugs' with rich mine matter. In 
this zone the ore was changed from oxides to sulphides, with blende 
predominating over the galenite. Below the 160-foot level the East 
vein again becomes richer in silver. * * * 

"For 160 to 200 feet the vein becomes still more steep. * * * 
Near the 200-foot level the West vein is 10 to 16 feet thick, and is 
filled with argentiferous galenite. * * * The East vein is di- 
vided by' a 'horse' at the 160-foot level. * * * Below the 200- 
foot level the blende gradually increases, and finally predominates 
over the galenite. * * * At 170 feet the richest ore was found 
in a lenticle in the general mass, 2 feet thick. * * * 

"Passing to the north along the East vein are the Symond's shafts. 
Sulphide ores were encountered here near the surface. 
Symond's east shaft was sunk 110 feet, and the west shaft 210 feet. 
* * * A level was driven from near the bottom of Symond's 
west shaft, running angling back to the Engine shaft in the East 
vein." 1 

Ore. — The ore is predominantly a complex mixture of sulphides, 
chiefly galena and sphalerite, with some chalcopyrite and pyrite; the 
whole carrying silver and a little gold. In the upper workings large 
bodies of carbonate ores, carrying high gold and silver values, have 
been encountered. From specimens on the dump, there appears to 
be little quartz associated with the ore. The gangue is chiefly the 

iNitze, H. B. C and Hanna, G. B. Gold deposits of North Carolina. N. C. Geol. Survey, Bull. 
3 (1896): 62-65. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XVIII. 




ORES AND MINES OF THE DISTRICT. 



103 



country rock; and some of the ore has a banded appearance, resem- 
bling the structure of the schists, as if the ore had replaced the rock. 

Upon the dump are found two interesting rock types, whose under- 
ground relations are not known. One is a grayish-green, tough rock 
composed of interlocking and radiating fibers of actinolite ; and prob- 
ably is a dike rock. The other is a dull, grayish-green, rather soft 
rock, which mashes to a white powder. By a hand lens it is seen 
to be made up of a green mineral and feldspar. The microscope 
shows it to be composed of numerous shreds of biotite in a fine 
granular aggregate of feldspar, with some quartz. Garnets are abun- 
dantly present. This rock is suggestive of contact metamorphism. 

A derjse, siliceous "hornstone" is found on the dump, and is often 
mineralized. This represents a silicified tuff or devitrified rhyolite, 
and is probably a part of the wall rock. 

Assays of ore. — The following is an average of 200 assays and 
will give some idea of the run of the ore i 1 





21.9% 


Pyrite 

Sphalerite 


17. 1% 
59. 2% 
00. 025% 


Chalcopyrite 


01.8% 




100. 025% 



Below is given the results of a sampling made of the mine in 
1898 by E. Hopkins, Engineer for the West Prussian Mining Com- 
pany. The numbers of the assays correspond to numbers in Plate 
XVT. 

ASSAYS OF ORE FROM THE SILVER HILL MINE. 



No. 


Description of Ore. 


1 

; Gold. 


Silver. 


Lead, 
per cent. 


Zinc, 
per cent. 


Copper, 
per cent. 


1 
2 


Mixed sulphides 

Silver rock 

Pyritic gold ore 

Pyritic gold ore 

Mixed sulphides 


I 

J $ 12.00 

-! 5.00 

. 191.00 

J 507.00 

. 8.02 

6.12 

4.67 

_ | trace 

trace 

1 


$ 17.94 

58.20 

44.40 

120. 00 

18.40 

57.60 

3.64 

4.08 

6.60 


15 


28 


i 


3 


10 

10 

17.69 

16.5 

19.47 

17.3 

13.0 






4 






5 


35 




6 


Mixed sulphides.. 




7 j Ore fr. 700 ft. level 


37 
39 

40 




8 
9 


Orefr. 700 ft. level 

Ore fr. N. shaft 


0.3 
estimated 



Equipment. — The mine has practically no equipment at present. 
The buildings, confined to a shaft house and a few small offices, are 
dilapidated. All the machinery has been either discarded or sold. 



iNitze, H. B. C, and Hanna, G. B. 
3(1896): p. 66. 



Gold deposits of North Carolina. N. C. Geol. Survey, Bull. 



104 THE CID MINING- DISTRICT OF DAVIDSON COUNTY. 

Silver Valley Mine. 

Location, — The Silver Valley Mine is situated 5 miles northeast 
of the Silver Hill Mine, and about 12 miles southeast from Lexing- 
ton. It occupies the western side of a small valley through which 
Flat Swamp Creek flows. 

History. 1 — This mine, for a short time known as the Spring Val- 
ley Mine, was discovered in June, 1880. Development work was 
immediately started and by the end of the same year a 10-stamp mill 
had been completed. The following year work was actively prose- 
cuted, 90 men being employed; and the lower grade ore was stamped 
and passed through 9 buddies. This treatment of the ore, which is 
a complex mixture of sulphides similar to the Silver Hill ore, evi- 
dently proved unsatisfactory, for in 1883 the shaft was allowed to 
fill with water. Up to December, 1882, 1,000 tons of ore and con- 
centrates were shipped. In 1884 no work was attempted, except to 
test two "double Rittenger tables," which had been installed the pre- 
vious year for concentrating the ore and separating the blende from 
galena. These also were found unsuitable, and no further work was 
done until 18 87. At that time the mine was reopened to supply the 
newly erected smelting works near Thomasville. This plant was 
organized by the North Carolina Smelting Company especially to 
treat the silver bearing ores of the Silver Valley Mine; but it was 
also hoped that the plant would furnish a near market for concen- 
tration of ores from a number of the smaller mines of the Appala- 
chian region. A tramway was constructed from the Silver Valley 
Mine to the smelting works. A small amount of the ore was shipped 
from the State for experimental purposes. 

The new smelting works did not prove a great success. In 1890 
an increase in the silver production of the State was reported, "due 
to the starting up of the North Carolina Smelting Works at Thom- 
asville." But evidently no satisfactory method of treating the ore 
was decided upon; for 1891 was taken up almost entirely in mak- 
ing tests on the Silver Valley ore, and in 1892 the plant passed into 
the hands of the New Jersey Smelting Company. After thorough 
overhauling under the new management, the plant was again in 
operation in 1893, when several hundred tons of ore from Silver 
Valley were used in admixture with ores from various parts of 
North Carolina. The treatment was said to be successful. The 

largely from the reports of the Director of the Mint, 1880-1894. 



ORES AND MINES OF THE DISTRICT. 105 

lead and zinc were separated as oxides and the precious metals went 
on the market as matte. The following year the operations were 
greatly abridged. 

In 1895 a "successful process was introduced by Mr. Nininger, 
of Newark, N. J. It consists of a down-draught jacket furnace, 
through which the fumes of lead and zinc are carried downward in 
condensers, where they are met by a spray of water, the liquor being 
led to vats where the lead oxide is deposited, while the zinc remains 
in solution and is subsequently precipitated as zinc oxide. The 
matte, carrying copper, gold, and most of the silver, is tapped from 
the well of the furnace and cast into pigs." x Shortly after 1895 all 
work ceased. 

No work has been done at the mine since 1893, except unwatering 
and cleaning out in 1903. 

Surface features. — The mine is situated in a complex formation 
represented by outcrops of sericite schist, slate, acid volcanic breccia, 
andesite, andesitic breccia, and acid fine tuff. Nearly every type of 
rock in the entire district is found within a half mile. In the imme- 
diate vicinity perhaps the most abundant outcrops are light colored 
schists, from their positions and relations regarded as mashed acid 
tuffs or breccias. The main vein is situated on the western bank of 
Flat Swamp Creek, and is entered by a vertical and an inclined or 
underlay shaft. Some work has been done on a quartz vein along- 
side a small branch flowing into Flat Swamp Creek and entered by a 
shaft 230 yards northeast of the main shaft. Some gold is said 
to have been panned for several hundred yards up the branch, and 
along its length are found old diggings and an abandoned shaft at 
which a little work was once done. 

Underground development 2 — The extent of development in the 
main vein up to 1883 is shown in the accompanying diagram (Plate 
XIX). The New West or Bashor shaft is now 210 feet deep. At 
the 150-foot level a drift extends south 200 feet and north 80 to 
100 feet. At 150 feet a cross-cut has been driven west 100 feet and 
east 20 feet. The bottom level runs north about 75 feet. The vein 
has a trend of about N. 35° E. and dips 45° to the northwest; in 
width it varies from 5 to 12 feet. It consists of bands of ore, quartz 
and country rock. The foot-wall is a brittle, fine-grained, siliceous 

iNitze, H. B. C, and Wilkins, H. A. J. Gold mining in North Carolina and adjacent South Appa- 
lachian regions. N. C. Geol. Survey, Bull. 10 (1897): p. 40. 
2 From statements by Mr. Alex. Hedrick, Superintendent in 1908, and from Nitze and Hanna. Gold 
deposits of North Carolina. N. C. Geol. Survey, Bull. 3 (1896): 66-68. 



106 



THE CID MINING DISTRICT OF DAVIDSON COUNTY 



rock, which is either a fine tuff or a devitrified rhyolite. The hanging 
wall is a schist, probably the mashed tuff or breccia, into which the 
vein grades without a definite, clear-cut boundary. The ore seams 
are from 3 to 18 inches thick. The Branch shaft, sunk on the 
small quartz vein to the northwest, is 80 feet deep, with a level run- 
ning northeast about 40 feet. The character of the ore here is about 
the same as in the main shaft. 

Ore. — The ore of the Silver Valley Mine is a complex mixture of 
galena, sphalerite, chalcopyrite and pyrite, carrying gold and silver. 
It is similar to the Silver Hill ore. From specimens' on the dump the 
ore occurs both in quartz and in the country rock. Quartz is appa- 
rently not an abundant gangue. 

The following table of assays will give some idea of the run of 
the ore: 

ASSAYS OF ORE FROM THE SILVER 
VALLEY MTNE.i 





36 


37 


38 


Gold, per ton 

Silver, per ton 


trace 

$ 17. 19 

15.54 

31.43 


% 4.13 
176.49 
55.25 
11.24 


trace 

% 38. 14 


Lead, per cent 


38.80 
32.00 







39 


40 


41 


42 


Poor 


Good 


2d cone. 


2d cone. 


] concen. 


cone. 


fr. 


fr. 






poor ore 


solid 



I 

Gold, per ton { $ 4.13 $ 4.13 

Silver, per ton | 23.01 | 44.74 

Lead, per cent j 11.18 j 47.62 

Zinc, per cent 27.70 j 12.68 



$ 1.03 |S 1-65 

13.08 ; 14.34 

9.63 I 8.13 

27.84 ! 33.54 



Assay No. 36 more clearly represents the common run of the slightly cobbed ore, and No. 38 the 
more massive ore. No. 37 is exceptional. The gold is not uniformly diffused; it tends to follow the 
pyrite. 

Equipment. — Most of the equipment of the mine has been sold. 
The shaft house is still standing, but the mill house is not in good 
condition. 

Welborn Mine. 

Location. — The Welborn or Smith mine is situated 2 miles west 
of Silver Hill and is not included within the confines of the geo- 
logic map. 



l Nitze and Hanna. Gold deposits of North Carolina. N. C. Geological Survey, Bull. 3. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XIX. 



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ORES AND MINES OF THE DISTRICT. 107 

History and description, — The Smith or No. 1 shaft was sunk in 
1882-83 to the depth of about 50 feet and a concentrating plant was 
installed. In 1883 several hundred tons of ore had accumulated on 
the dumps and an attempt was made to smelt it. The reduction pro- 
cess proved unsatisfactory and the mine was closed in June, 1883. 
The mine is reported to have produced 6-8 tons of ore per day, 
assaying high in silver and gold. 1 During the course of the work, 
another shaft, the Miller shaft, was sunk about one-fourth mile 
southwest of the No. 1 shaft. 

The country rock is a dark blue to green, badly mashed schist. 
Some facies are clearly fragmentary, this feature appearing espe- 
cially well upon the weathered surface. The rock doubtless repre- 
sents an andesitic tuff or breccia. The vein consists of narrow, 
lens-like intercalations of' quartz in the country rock, and having 
in common with it a strike of N. 25° to 30° E. and a dip of 
20° to the northwest. The ore is a complex mixture of galena and 
sphalerite, similar to the Silver Hill ore. 

The mine has been abandoned and is overgrown with bushes and 
underbrush. ]STo ore can be found on the old dump. A few hun- 
dred yards away is the remains of an old furnace and concentrat- 
ing plant. 

Nooe Mine A 

The Nooe mine is situated about 3 miles north of Silver Hill, 
and off the confines of the geologic map. In 1880 a shaft was sunk 
to the depth of about 60 feet and a "baugh" gold mill was erected, 
in which the ore was crushed in stone breakers and rollers, roasted, 
pulverized, and amalgamated in tubs. The plant is stated to have 
run only about two months. The remains of the mill may still be 
seen on the property. 

The country rock is a dark blue schist, striking N. 35° E. with 
a vertical dip. It appears to be fragmental in character and prob- 
ably represents a mashed andesitic tuff. The vein matter averages 
3 feet in thickness and consists of quartz stringers, containing lenses 
of ore, distributed in the country rock. The ore is a mixture of 
galena, sphalerite, pyrite, with a little gold and chalcopyrite. Spha- 
lerite is the most abundant constituent of the mixture. 

The mine is now abandoned. 



^Reports of the Director of the Mint in 1882: 625. 



108 THE CID MINING- DISTRICT OF DAVIDSON" COUNTY. 

Ida MineA 

The Ida mine is situated 1J miles a little east of north from the 
Silver Hill mine, and in the same belt of sericite schists. A shaft 
was sunk in 1878 to the east of a large quartz vein which showed 
upon the surface. A cross-cut was driven into the foot-wall for 
about 60 feet, but the quartz vein was not encountered. The coun- 
try rock is a sericite schist, trending iN". 20° E., with a dip of 65° 
to the northwest, and has some pyrite disseminated through it. The 
shaft is now abandoned and caved. 

Sechrist Mine. 

The Sechrist mine is situated 1-| miles northeast of the Silver 
Hill mine in a belt of arjdesitic breccia. A shaft was sunk on a 
large outcrop of quartz carrying pyrite and lead, but little or no 
ore was encountered, and the prospect was consequently abandoned. 

Baltimore Mine. 2 

The Baltimore mine is situated about three miles north of Silver 
Hill, off the boundaries of the geologic map. It was prospected 
long before 1880. About 1880 it was cleaned out and retimbered 
61 feet to the bottom; and a little drifting was done to the north. 
Stoping previously done to the south had caved and was not dis- 
turbed. A few tons of ore were taken out. ~No work has been 
done since. 

Free-milling brown ore was found to a depth of 60 feet. Below 
that level pyrite, carrying a little chalcopyrite, galena, and gold was 
encountered. The shaft goes down on a quartz vein about 3 feet 
in width. 

THE CONEAD HILL TYPE. 

Conrad Hill Mine. 

Location.- — The Conrad Hill mine is situated 6 miles east of Lex- 
ington and about 6 miles a little east of north from Silver Hill. 
Its location is not shown upon the geologic map, but the eastern edge 
of the map, if extended one mile, would include the mining property. 
It occupies the top of a well-rounded hill, rising with gentle slopes 
100 feet or less above the adjacent valleys; and separated from 
Three Hat Mountain to the east by a rather prominent valley. 

^rom information kindly given by Mr. J. A. Shirley of Silver Hill and from the observations of 
the writer. 

2 Largely from information kindly furnished by Mr. J. F. Peters of Silver Hill. 



ORES AND MINES OF THE DISTRICT. 109 

History.— The Conrad Hill mine was discovered and worked 
prior to 1853, for J. D. Whitney 1 mentions having visited the mine 
in that year, at which time two well-timbered shafts, 115 and 100 
feet deep, had been sunk. The mine was first worked profitably for 
gold in the upper parts of the veins, but soon sulphides were reached 
and copper found to be the most important metal. Little can now 
be ascertained of work carried on between 1853 and 1880. The 
mine, however, was probably closed for the greater part of that time. 
In 1880 it was reopened, and for some years rather extensive opera- 
tions were carried on. Two stack furnaces were in process of erec- 
tion, 150 men were employed, and four veins were worked, with the 
workings extending to the depth of 250 feet. The "Hunt and Doug- 
las process" was successfully applied to the treatment of the ores. 
"The roasted sulphurets were leached with a ferrous chloride solu- 
tion, converting the copper to a soluble chloride, from which it was 
precipitated as metallic cement on scrap iron." 2 Between 1880 and 
1882, $125,000 is reported to have been expended chiefly upon 
equipment. 3 In 1882 the production was larger than for any other 
mine in the State. In that year the equipment was as follows : 
4 5-stamp batteries with necessary concentrating machinery ; melting 
furnace of a capacity of 10 tons per day; roasting shed with a 
capacity of 100 tons ; 4 reverbatory furnaces ; plant for the chemical 
treatment of copper ore, including 8 solution tanks and precipitation 
vats. 4 With the completion of the stack furnaces the ore was treated 
by "matte smelting," followed by refining in the reverbatory furnaces. 
This process was not found economically advantageous ; consequently 
in 1883 the Hunt and Douglas process, with some modifications, was 
adverted to, and for a time found successful. In the same year the 
20-stamp mill was remodeled, and the copper amalgamating plates 
were in part replaced by "Moore's wave plate amalgamator," said to 
have been useful in saving gold. 5 The underground work was car- 
ried forward and Dodge Hill, an adjoining property, was acquired 
and prospected. Within the next few years the mine must have 
closed, for no further mention of it as a producing mine is found, in 
the reports of the Director of the Mint. The mine was un watered 
in 1907 and a small amount of ore was gotten out; but nothing 
was shipped. 

iWhitney, J. D. The metallic wealth of the United States * * * 1854: 130. 
2Nitze and Wilkins. Gold mining in North Carolina and adjacent South Appalachian regions. 
N. C. Geol. Survey, Bull. 10 (1897): 39. 

3 Balch, W. R. Mines, miners, and mining interests of the United States in 1882. p. 1120. 
^Report of the Director of the Mint for 1882, p. 625. 
HUd. for 1883, p. 648. 



110 



THE CID MINING DISTRICT OF DAVIDSON COUNTY. 



Surface features. — The country rock is a light gray to cream- 
colored, badly mashed, fine-grained acid tuff, with bedding planes 
not corresponding with the schistosity. The rock might more prop- 
erly be called a sericite schist. The veins are several in number 
and occupy the crests of both Conrad Hill and Dodge Hill. Their 
distribution is shown on the accompanying map (Fig. 4). 



DODGE HILL 




MAP OF CONRAD HILL 

by 
W, E P o <j a e ? (Jr. 


/ 


& uartz vein 


5? 


J haft 


>? 


prospect 





Engine sh. 


© 


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Fig. 4 — Map of Conrad Hill Mine, Davidson County, N. C . 

The above map gives only in a general way the surface trace of 
the most prominent veins. An accurate plotting is impossible from 
the surface features alone; for in many cases instead of being well 
defined veins, they are great masses of quartz in the mashed and 
oftentimes shattered country rock. In such instances the trend of 
the vein is largely a matter of inference from the alignment of the 
prospect holes. Sometimes the fragments of the country rock are 
separated from each other by quartz, giving the appearance of a 
breccia. The veins have been described by Nitze and Hanna 1 as 
follows: "There are two systems of veins traversing the hill; one 

^Nitze, H. B. C, and Hanna, G. B. The gold deposits of North Carolina. N. C. Geol. Survey, 



ORES AND MINES OF THE DISTRICT. Ill 

consists of veins parallel to each other and to the strike of the 
-schists, while in dip they frequently, perhaps it may be said gener- 
ally, cut the schistosity at a slightly more westerly angle. The sec- 
ond system differs from the first in being entirely independent of 
each other and of the country rock, in strike and dip." 

Underground development. — It is difficult to ascertain the exact 
amount of underground work done. The following is taken almost 
verbatim from Nitze and Hanna's report: 1 

There are four shafts sunk in the property, as shown in the map 
(Fig. 4). In the Eo. 1 shaft a large body of ore was entered at 
the depth of 98 feet. At the depth of 105 feet a drift was run some 
40 feet north and 90 feet south along and in this body of ore, 
exposing a thickness of 5 to 10 feet, all of which is stated to contain 
gold in paying quantities. In the lowest part of this mass of ore, 
the richer portion, about 4 feet wide, separated from the remainder 
of the vein by a well-defined line of demarcation, will assay high up 
to $300 per ton. Just south of the shaft a cut has been made from 
the drift, across this body of ore, measuring some 37 feet, to the 
foot-wall, giving a thickness of about 20 feet. A large part of this 
thickness is composed of crushed country lock, filled with stringers 
of quartz. A sample taken across this section, including country 
rock, quartz, and everything representing the whole body of the vein, 
yielded $22.73 per ton. 

In the No. 2 shaft two veins intersect at a depth of 67 feet. 
A cross-cut has been driven 67^ feet into the veins, exposing on the 
southeast side of the drift a course of gold and copper ores varying 
from 18 to 24 inches in thickness. At a depth of 100 feet a drift 
has been carried some 50 feet south in a mass of ore assaying $13.39 
per ton. Some 40 feet north of this shaft, on the same level, a simi- 
lar ore course of 12 to 20 inches of 33 per cent copper is exposed 
toward the upper part of the vein, while a stope driven up and along 
the middle of it, in brown oxide and iron carbonate, gives, by assay 
of sample representing a thickness of 3 feet, $17.38 per ton for gold. 

The Engine shaft is situated 195 feet west of the No. 1 shaft, 
and is distant 240 feet from the No. 2 shaft. It was sunk 220 feet 
vertically, and subsequently to 400 feet. At 163 feet the shaft 
passes through the main cross vein. Throughout the entire distance 
a rich course of copper ore is exposed from 3 to 8 feet in thickness, 

iNitze, H. B. C, and Hanna, G. B. The gold deposits of North Carolina. N. C. Geol. Survey, 
Bull 3 (1896): 70-72. 



112 THE CID MINING- DISTKICT OF DAVIDSON COUNTY. 

of which 1 to 4-J feet is solid prill (i. e., 33 per cent copper) ore, 
giving an average of not less than two feet. Samples taken from 
across the whole face, and assayed by Hanna, give $11.98 gold per 
ton in addition to their copper value. 

Ore. — The ore of the mine is pyrite and chalcopyrite, carrying 
gold. It is distributed irregularly throughout the veins, but judg- 
ing from small specimens on the dump, seems to be often concen- 
trated into definite portions of the vein. All the ores are said to 
carry gold, but to vary greatly in value. The upper workings carry 
limonite and rarely a little specular hematite. The gangue is 
quartz, siderite, and in rare instances a little chlorite. This last 
appears to occur near the walls of the veins, and is not essentially 
a gangue. Oftentimes there is a definite alteration or banding of 
quartz and siderite. Again the siderite is distributed irregularly 
through the quartz. The quartz is often subsequent to the siderite ; 
at times the two are contemporaneous ; rarely the quartz appears to 
be older. About 30 per cent of the gangue is estimated to be siderite. 

Equipment. — The mine is equipped as follows : Boiler, hoist, 
etc. ; old stamp mill, with 20 stamps, 10 of which are in fair repair ; 
remains of a smelter ; numerous smaller buildings and houses not 

in good repair. 

Peters Mine. 

Location. — The Peters Mine is situated 2 miles south of east from 
the Silver Hill Mine. 

History. 1 — The first work at this locality was done about 1830. 
Only a prospect shaft was sunk at that time and work was on a small 
scale. A little work was also done before and during the period of 
1861-65. In 1901 work was resumed, and a shaft was put down to 
a depth of 60 feet. In 1902 the present plant, consisting of a shaft 
house and small mill, was erected, and the shaft deepened to 85 feet. 
Several levels were run, but little stoping was done. About 200 
tons of ore were concentrated at the mill, and the gold separated, 
which was sent to Charlotte. Work was stopped in 1904. 

Surface features. — The country rock is a sericite schist, and part 
of the belt that extends past Silver Hill to Conrad Hill. Two 
nearly parallel gabbro dikes with a northeast trend pass only a few 
hundred yards on either side of the mine. Considerable prospect- 
ing has been done on a series of quartz veins which extend in a line 

According to Mr. J. F. Peters of Silver Hill. 



ORES AND MINES OF THE DISTRICT. 113 

1|- miles southwest of the Cross Mine, and form the mineralized 
zone upon which the two mines are located. This must not be con- 
sidered a continuous, well-defined vein;- but rather, a narrow band 
of the schist which has been mineralized and silicified, and had 
introduced into it parallel to the schistosity a large number of quartz 
veins, lenses, and seams. 

Underground development. — The underground workings are 
shown in the accompanying plan (Fig. 5). The vein, which has a 
strike of about ~N, 45° E., varies from 3 to 7 feet in width, with an 
average of 4 feet. Little stoping has been done. The upper levels 
down to 60 feet carry free-milling ore. 

Ore. — The ore is chalcopyrite, with pyrite, and carries gold. 
The gangue is quartz and siderite. From specimens on the dump, 
the chalcopyrite and pyrite occur scattered through the quartz and 
enclosing fragments of it, as if the quartz had been brecciated pre- 
vious to the deposition of the ores. Siderite is apparently less 
abundant than the quartz ; seams and bands occur in the quartz and 
are probably later than the siderite. Talc is sparingly present, and 
is usually near the walls. The ore is stated to run about $11 in 
gold per ton; its copper value is not known. 

Equipment. — Upon the property is a shaft house, connected by 
a tramway to a small mill. The shaft house is equipped with a 10 - 
horsepower hoist; 15-horsepower boiler; and an Emeison vacuum 
pump. The mill contains 2 Tremain stamps ; 1 Wilfley table ; 12- 
horsepower engine; 35-horsepower boiler; small Blake crusher, with 
8 by 10-inch opening; and a lj-horsepower engine for running the 
table. The ore is crushed, stamped, passed over amalgamating 
plates and on to the concentrating table. 

The buildings and machinery are in good condition. 

Cross Bline. 

Location. — The Cross Mine is situated 1| miles southwest of the 
Peters Mine. 

History and description. — This mine was discovered a short while 
before 18G0 and prospected during 1860-65. A shaft was sunk 
to the depth of 50 feet. In 1904 the shaft was deepened to 75 feet, 
and some exploitation work carried on. Work was stopped the 
same year. 

Oxidized ores carrying free-milling gold are stated to extend to 



114 



THE CID MINING DISTRICT OF DAVIDSON COUNTY. 




ORES AND MINES OE THE DISTRICT. 115 

the depth of 70 feet and to average about $20 per ton. The shaft 
goes down on a quartz vein 6 to 18 inches in width. 

The equipment consists of a shed and a 1-horse whim. 

THE EMMONS TYPE. 

Emmons Mine. 

Location. — The Emmons Mine is situated 15 miles southeast of 
Lexington, and about 1 mile south of Cid. 

History. — This mine, formerly known as the Davidson Mine, was 
discovered and worked prior to 1861, but was closed during the 
Civil War. Shortly after it was reopened and worked several years 
by a Baltimore company. For treating the ores, the Hunt and 
Douglas (old) process was used successfully for a long period. In 
1885 and 1886 the mine was again operated for a short time. In 
1902 development work was carried on, and in the following two 
years considerable ore was blocked out and a complete concentrating 
plant installed. The mine has not been actively operated between 
that time and 1909. 

Surface features. — The country rock is a dark greenish-blue, 
schistose slate, with bedding planes cutting the schistosity at a 'small 
angle. The outcrops strike about N. 30° E., with a dip varying 
from 40° to 70° northwest. Intercalated with the slate in the im- 
mediate vicinity of the mine appear outcrops of greenstone schists, 
which doubtless represent lenses of mashed andesitic tuff. Within 
a mile of the mine may be found areas of -dacite, rhyolite, gabbro, 
and acid and basic breccias. The veins are not well defined upon 
the surface, though mineralization is indicated by the highly colored 
character of some of the outcrops. There are a number of old dig- 
gings and shafts in the vicinity; but most of the work has been 
confined to two veins. The westernmost of these is entered by the 
Main or Engine shaft and the North or No. 2 shaft. About 100 
yards to the east, the second vein is entered by the No. 3 shaft. 

Underground development — The longitudinal section of the 
underground workings in the main vein up to November, 1908, is 
•shown in the accompanying plan (Plate XX). "The vein is paral- 
lel to the slates and consists of irregular stringers of quartz, often 
cutting into or surrounding masses of slate. These carry consider- 
able chalcopyrite and pyrite, sometimes mostly one, and sometimes 
the other. The included and adjoining slates are also mineralized, 



116 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

but there is usually but little chalcopyrite outside the last ribbon of 
quartz, but sometimes there is very little quartz in the vein. Mr. 
Cockreham, the superintendent, thinks that the gold follows the 
quartz. There is no selvage along the walls and at least one of them 
is very irregular. The ore is generally 2 or 3 feet thick, but in one 
place it is 12. feet, and the vein is often very narrow. There is no 
ore south of the main shaft, and the richest shoot is the one that has 
been continuously stoped, just north of the main shaft. The widest 
one is just beyond the North or No. 2 shaft, and there is a very long 
body of ore on the 200-foot level, reaching nearly from shaft to 
shaft. There is ore in the No. 2 shaft to within 30 feet of its bot- 
tom, where it becomes lean and quartzy. Most of the 280-foot level 
is barren beyond the main shoots, although there is some ore in the 
upper part of the upraise. On this level the main shoot is not quite 
so long or so wide, but is a little higher grade. In the breast of 
this level there is a little ore in quartz. * * * The ore, mined 
chiefly from the good shoot, runs from 3 to 4 per cent copper. 7 ' 1 The 
ore to the north and to the south of the North shaft runs about lj 
to 1 J per cent copper. 

The west vein is entered by the No. 3 shaft, which extends to a 
depth of 170 feet. The 90-foot level runs south for about 25 feet 
and north about 10 feet. The vein varies from 1 to 4 or 5 feet in 
width, with an average of about 18 inches, and consists of stringers 
of quartz in a greenstone schist. Chalcopyrite occurs both with the 
quartz and in the schists. 

Ore and gangue.— The ore in the main vein is chalcopyrite, with 
some galena, sphalerite, and pyrite, and carries a small gold content. 
The gangue is siderite, chlorite, and. calcite. The ore shoots are 
said to pitch to the southwest. 2 From ore picked up from the 
dump, the following features are noted: Quartz stringers are paral- 
lel to and cut the schistosity; much of the country rock shows 
slickensides ; pyrite impregnates much of the otherwise barren rock; 
chalcopyrite occurs both with the quartz and in seams in the schists ; 
calcite is rarely found and is never abundant; chlorite tends to 
accompany the barren quartz. 

The following features were noted from the dump at the No. 3 
shaft: Much calcite is present along with the quartz as a gangue; 
chalcopyrite occurs in the quartz, in the calcite, and in the country 

iRtPel A A and Pratt, J. H. Recent changes in gold mining in North Carolina. (In the mining 
industry in N. C. for 1906.) N. C. G. S., Ec .Pa 14: 39-40. 

2Nitze and Hanna. Gold deposits of North Carolina, p. 60. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XX. 









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ORES AND MINES OF THE DISTRICT. 117 

rock ; at places seams of calcite traverse the quartz ; in one specimen 
small scales of talc are associated with the calcite; slickensides are 
abundant, and occasionally pyrite cubes are mashed and drawn out on 
a slickensided surface; the seams and veins of calcite are buth 
parallel to the schistosity and ramify irregularly through the rock; 
chlorite is often present in the quartz, but is usually not associated 
with the ore. 

Value of the ore. — A representative car load of concentrates is 
stated to have given the following smelter returns : 7.7 per cent cop- 
per, 1.27 ounces silver per ton, and 0.10 ounces gold per ton; for 
which was paid $31 per ton, with a charge of $12.80 a ton for 
smelting and sampling. 1 

Equipment. — The mine is equipped with shaft house, mill, smel- 
ter, and a number of smaller buildings, all in good condition. The 
grounds and plant are well cared for, and work could be resumed at 
any time on short notice. The Hercules Gold and Copper Com- 
pany, of New York City, are the present owners of the property, 
which includes a tract of 400 acres, and the Cid Mine and property 
of 45 acres. 

The mill is equipped with a Blake crusher, feeders, 10-stamp bat- 
tery, 8 Wilfley tables, classifier, and a Deister table. Its capacity 
is 50 tons in 24 hours. (See Plate XXI, A and B.) 

Cid Mine. 

Location. — The Cid Mine is situated 1J miles northeast of the 
Emmons Mine, and in a continuation of the same belt of rock. 

History and description. — It was discovered during or before 
1882 ; by December of that year a shaft had been sunk 20 feet. 2 
The mine was worked at intervals for a few years. Gold was at 
first sought, but with little success, and attention was directed to the 
copper ores. For some reason work was stopped after the sinking 
of an underlay shaft to the depth of 100 feet. r In 1903 the mine 
was operated on a small scale for a short time. 
. The country rock is a dark greenish-blue, bedded slate, Tjuth lenses 
of greenstone schist. The vein is not prominent on the surface. 
The ore is chalcopyrite with pyrite, carrying some silver and a little 
gold. The mine is at present without shaft house or equipment. 

iSteel, A. A., and Pratt, J. H. Recent changes in gold mining in North Carolina. (In the mining 
industry in North Carolina during 1903.) N. C. Geol. Survey, Ec. Paper 14 (1907): 41. 
2 Report of the Director of the Mint for 1832: p. 625. 



118 THE CID MINING DISTRICT OE DAVIDSON COUNTY. 

Ward Mine. 1 

Location. — The Ward Mine is situated 2 miles east of Cid on the 
crest of a small knoll. 

History. 2 — Gold was discovered at this mine shortly before 1853, 
and surface work was carried on at intervals until about 1882. At 
this time a shaft was sunk to a depth of about 60 feet, and some 
exploiting was done. About 1890 the surface was again worked 
with crude appliances, the shaft deepened about 25 feet, and a cross- 
cut run east for a short distance. Between 1895 and 1905 further 
surface work was done ; a 20-stamp mill was erected and the shaft 
retimbered. Only a small quantity of ore was mined and the mine 
was allowed to fill with water. 

Description. — The mine has been worked entirely for gold, which 
occurs very irregularly distributed through a large mass of quartz. 
It is with difficulty that the great abundance of quartz which appears 
upon the surface can be traced into definite veins; it more probably 
represents a number of intersecting quartz masses and numerous 
stringers and lenses, with no well defined alignment or walls. There 
may be one vein running about N. 25° E, and another E. and W. 
The country rock is a mashed acid tuff, with some slate just east of 
the shaft. Upon the knoll, in close connection, with the quartz, 
occurs a light gray, massive rock, which may represent a rhyolite or 
an acid tuff, probably the latter. This is filled with small quartz 
seams, said to carry good gold values. 

"A very large proportion of the gold is crystalline. The pockets 
containing crystals usually lie in a red, siliceous clay, which has been 
derived from the rock in contact with a seam of quartz. Some of 
the pockets have furnished 500 or 600 dollars of crystallized gold." 3 
Gold is said to have been abundantly panned just west of the 
small rise and along a little stream. There are many pits in this 
area, indicating rather extensive surface workings. The mine seems 
to warrant some further surface work; hardly enough development 
has been done to show up the nature of the vein and its richness. 

FEATURES OE THE ORE DEPOSITS. 

Certain features of the ore deposits which have a special bearing 
on origin will here be summarized. It is regretted that lack of 

iThia mine is described at this place for convenience, rather than because it might be strictly clas- 
sified under the Emmons type of deposit. 

^According to Mrs. A. J. Gillingham, owner in 1909. ■ 

'Emmons, Ebenezer. Geological report of the midland counties of North Carolina. Raleigh 
(1856): 138. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATE XXI. 




A. Shaft houses at emmons mine. 




B. Mill and smelter at emmons mine. 



ORES AND MINES OF THE DISTRICT. 



119 



direct underground observations necessitates that this account be 
brief and of a general nature. 



LIST OF MINERALS. 



A list of the minerals constituting or accompanying the ore de- 
posits is given below, together with the names of the mines in which 
they are found. 



LIST OF MINERALS CONSTITUTING OR ACCOMPANYING THE ORE 



Ore Minerals: 



Gangue Minerals: 



DEPOSITS. 

Anglesite Silver Hill • 

Argentite Silver Hill. 

Calamine Silver Hill. 

Cerussite Silver Hill. 

Chalcanthite Silver Hill. 

Chalcopyrite All the mines. 

Chalcolite Silver Hill. 

Cid. 

Cuprite Silver Hill. 

Galena •_ Emmons. 

" _ Silver Hill. 

" Silver Valley. 

" , Welborn. 

" Nooe. 

" Ida. 

" S'echrist. 

" Baltimore. 

Gold All the mines. 

Goslarite Silver Hill. 

Linarite Silver Hill. 

Malachite All the mines 

Tenorite Silver Hill. 

Pyrite All the mines. 

Pyromorphite Silver Hill. 

" Silver Valley. 

Silver (native) Silver Hill. 

Stolzite Silver Hill. 

Sphalerite Emmons. 

" Silver Hill. 

" Silver Valley 

" Welborn. 

" Nooe. 

" Ida. 

" Sechrist. 

"_.--*. Baltimore. 

Actinolite Silver Hill . 

Calcite Emmons. 

Chlorite Emmons. 

" Conrad Hill. 

Hem atite Conrad Hill . 

Orthoclase Silver Hill. 

Quartz All the mines. 

Siderite j Conrad Hill. 

" Silver Valley. 

" Peters. 

" Cross. 

Talc Peters. 

" Emmons. 

Wavellite : Silver Hill. 

Zoisite Silver Hill. 



Description of Ore Minerals. 
Gold occurs in all the deposits ; it may be free in the quartz, or 
closely associated with pyrite, or disseminated through the surface 

U. S. Geol. Survey, 16th Ann. 



lAfter Becker, G. F., Gold fields of the Southern Appalachians 
Report, pt. 2 (1895): 28, with additions by Joseph Hyde Pratt. 



120 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

oxidized ores. Some of the gold found at the Ward Mine is well 
crystallized. Pyrite is an extremely common ore mineral, and 
generally carries a gold value; it occurs alone in the schists or in 
association with chalcopyrite. Galena and sphalerite are found as 
an intimate mixture in the mines of the Silver Hill type. In such 
deposits there is also almost invariably a small amount of pyrite and 
chalcopyrite present; and the whole mass carries a silver and gold 
value. Galena and sphalerite in small quantities are found in the 
Emmons Mine. Carbonates of lead and zinc, carrying native silver, 
have been taken in some quantity from the upper workings of the 
Silver Hill Mine. The other ore minerals mentioned in the table 
above are unimportant commercially. 

Description of Gangue Minerals. 

Quartz is the most abundant gangue mineral, and occurs both in 
well-defined veins and as lenses and stringers in the schists. It is 
also found as infiltrated silica in zones which are sometimes mineral- 
ized to the extent of being worked as veins. Siderite is an important 
gangue at the Conrad Hill and Peters mines, where it is nearly as 
abundant as the quartz. Calcite is abundant in ore from the No. 3 
shaft of the Emmons. Limonite, from the oxidation of pyrite, is 
present in all the surface ores; and in the Conrad Hill Mine hema- 
tite is also found in the upper workings. Often the country rock 
of the mines, usually a sericite or greenstone schist, or a dense, 
siliceous rock ("hornstone"), is in such intimate association with 
the vein-stuff as to be essentially a gangue. 

DESCRIPTION OF THE VEINS. 

The "veins" of the district are apparently of four kinds. These 
are not well-defined types ; nor can they be completely described or 
established. It is believed, however, from all available evidence and 
from the careful descriptions given by Becker, 1 Graton, 2 and Laney 3 
of veins occurring in other parts of the Appalachian region, that 
such a division is warranted. The "veins," or more properly, the 
mineralized zones, are accordingly grouped as follows: 

1. Impregnations, or stringers of ore in the schists, with little or 
no quartz. The ore is pyrite, carrying finely disseminated gold, and 
usually mixed with more or less chalcopyrite. This type is espe- 

iQold fields of the Southern Appalachians, pp. 25-43. 

2 A reconnaissance of some gold and tin deposits of the Southern Appalachians, pp. 59-61. 

5 The Gold Hill mining district, pp. 138-141. 



ORES AND MINES OF THE DISTRICT. 121 

cially well developed in the Emmons Mine ; though it seems to be 
present to a less degree in all the mines. It is apparently a subor- 
dinate accompaniment of the ore deposition. 

2. Stringer leads, or lenses and seams of quartz conformable with 
the schistosity or cutting that structure at small angles. These make 
up mineralized zones or lodes, which vary from a small number, of 
stringers in much country rock to large lenses of quartz, or true 
quartz veins, associated with only a few stringers. The whole mass, 
both quartz and country rock, is often mineralized and worked as a 
single "vein." Impregnations and stringer leads always occur asso- 
ciated. It is believed that the Emmons "vein" is a combination of 
the two types. The Conrad Hill and Peters mines are further ex- 
amples of the same thing; though there is here probably less im- 
pregnation than in the case of the Emmons, consequent upon the fact 
that the quartz veins in the former two mines are prominent and 
well developed. (See Plate XXII, A.) 

3. Cross veins, or well-defined quartz veins, which cut across the 
schistosity at large angles, presumably following joint directions. 
These are the veins which outcrop most abundantly and prominently 
upon the surface, and unfortunately are usually barren. The Con- 
rad Hill Mine is the only mine in the district in which these cross 
veins have been exploited at depth. The descriptions of this mine 
are not very detailed, but it appears that at the intersections of the 
cross veins with the "right running veins" (or veins nearly conform- 
ing with the schistosity) occur segregations of the ore, and that the 
other portions of the cross veins have been little worked and are 
presumably barren or nearly so. 

4. Replacement deposits, or zones carrying seams and lenses of 
ore with little or no quartz, and in a country rock extremely meta- 
morphosed or highly silicified. The ore is a mixture of galena and 
sphalerite, with pyrite and chalcopyrite, the whole carrying silver 
and gold. This type is represented by the Silver Hill, Silver Val- 
ley, and related mines. Such deposits can not definitely be shown 
to be due to replacement, although they are clearly different from 
the three first mentioned types. Great solid pieces of ore found on 
the dump suggest strongly that they have originated from a substi- 
tution of the schist by ore matter, so as to preserve the original struc- 
ture of the rock. These deposits, moreover, are found in highly 
schistose rocks of a tuffaceous character, such as from their porous 



122 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

nature would have afforded an easy path for solutions. On the 
dumps at Silver Hill and Silver Valley is found an abundance of 
u hornstone," which is likely a silicified tuff, and as such would be 
indicative of a vigorous circulation. Pieces of this rock contain 
narrow seams of ore, so that impregnation also went on to a certain 
extent. The deposits of the Silver Hill type were introduced by 
waters carrying a high silica content, because the country rock is 
highly silicified. Yet, while large deposits of metallic compounds 
were formed, very little free quartz was deposited. This is cer- 
tainly suggestive of country rock conditions favorable for an inter- 
change of elements so as to form metasomatic deposits, rather than 
for direct deposition by precipitation ; in which case, abundant quartz 
as a gangue would be expected. 

PARAGENESIS. OE ORDER OF FORMATION OF THE ORES. 

By means of a microscopic study of polished sections of typical 
ores from the Silver Hill, Silver Valley, and Emmons mines, the 
following relations of the sulphides have been ascertained. For this 
work an ordinary microscope, with double-eye piece, was used. The 
illumination consisted of an acetylene light, the rays from which 
were filtered through a pale blue cobalt glass and reflected down upon 
the polished sections. This source of illumination is stated to be 
practically identical in its effect with daylight. 1 Both polished and 
etched sections of the ores were studied. 

ORE FROM THE SILVER HILE MINE. 

Macroscopic description, — The ore from this mine consists of an 
intimate mixture of massive galena, sphalerite, and chalcopyrite. 
with a small amount of pyrite, the whole carrying a silver and gold 
value. The mixture is so intimate and so fine in texture, that little 
can be seen with the unaided eye as to the relation of the different 
minerals to one another. A rough and irregular banding of the 
minerals is usually seen. A band may be noted in which galena is 
the prevailing mineral ; then one of sphalerite ; and this in turn fol- 
lowed by one in which chalcopyrite prevails. There is, so far as 
noted, no regular succession of these bands, nor do they possess any 
degree of regularity as to width. 

Microscopic description. — The microscope shows the mixture to be 

Wright, Fred. Eugene. Artificial daylight for use with the microscope. Am. Jour. Sci., v. 27 
(1909): 197. 



N. C. GEOLOGICAL AND ECONOMIC SURVEY. 



BULL. 22, PLATEIXXII. 




A. The "stringer lead" type op vein, showing stringers and 

SEAMS OF QUARTZ AND ORE IN A SCHISTOSE COUNTRY ROCK. 
THIS IS A PHOTOGRAPH OP A POLISHED SEC- 
TION OP THE VEIN IN THE GOLD 
HILL MINE. THE EMMONS 
VEIN IS VERY SIMILAR. 




B. Photomicrograph of silver hill ore; 40 diameters; section 

POLISHED AND ETCHED BY CONC. HNO3. SCRATCHED AREAS ARE CHAL- 
COPYRITE. CLOUDED AREAS ARE galena (deeply etched). 
LONG SHREDS ARE AN AMPHIBOLE, PROBABLY ACTINOLITE. 
SECTION ALSO CONTAINS A LITTLE SPHALERITE. 



ORES AND MINES OE THE DISTRICT. 



12; 



even more intimate than the macroscopic examinations indicate. 
Each mineral is seen to have its own clear-cut and definite bounda- 
ries. There is absolutely no gradation of one into the other. The 
bands in which one mineral predominates over the others are seen to 
be still an intimate mixture of all the minerals, with only one in 
greater abundance. The areas between the bands and other irregu- 
lar areas which occur throughout the specimens consist of a most 
intimate mixture of very small and irregular grains of all the three 
sulphides, with now and then a speck of pyrite. These grains have 
the most irregular form conceivable, and interlock in the most intri- 
cate manner. A few fair-sized areas of pyrite occur. When these 
are placed under the miscroscope, they are seen to possess a spongy 
appearance and to be literally filled with small and irregular par- 
ticles of the other sulphides. Around the borders of the pyrite the 
other minerals are crowded together, and it appears as if the pyrite 
crystal in growing had pushed aside the greater portion of the other 
minerals. There were, however, small amounts of these which it 
could not throw out, and these it engulfed. A few shreds of an 
amphibole, perhaps actinolite, generally sheaf-shaped or radiating in 
appearance, were intimately mixed with the sulphides. Some areas 
of sphalerite are darker in color than others. (See Plate XXII, B.) 
From the foregoing examination, it is highly probable that the 
four sulphides are contemporaneous in origin. The solutions may 
have varied slightly in composition from time to time, and thus the 
rough banding may be accounted for. This feature, however, is more 
indicative of replacement. 

ORE FROM THE SILVER VAELEY MINE. 

The ore available for study was largely sphalerite, but carried 
small amounts of chalcopyrite and galena, with very little pyrite. 
The specimens were not satisfactory for microscopic examination, 
but everything seemed to indicate a contemporaneous origin for the 
■sphalerite, chalcopyrite, and galena. Nothing definite can be said 
as to the relation of the pyrite to the other sulphides. 

ORE FROM THE EMMONS MINE. 

Macroscopic description. — The ore from this mine is a mixture 
of chalcopyrite and pyrite, carrying a small gold value. 

Microscopic description. — The pyrite, for the most part, is appa- 



124 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

rently older than the chalcopyrite, but at times it seems to be con- 
temporaneous or even younger. The chalcopyrite very often is seen 
filling cracks and irregular areas in the pyrite, or completely sur- 
rounding pieces, apparently rough crystals of pyrite, in such a man- 
ner as to strongly suggest a breccia of pyrite in a matrix of chalcopy- 
rite. There is, however, in the sections examined, no very strong 
evidence as to the respective ages of the two minerals. Each mineral 
always has its own definite and distinct boundaries. There is no 
such thing as a cupriferous pyrite; it is a mixture of the two sul- 
phides, chalcopyrite and pyrite. No free gold was visible in any of 
the ores examined. 

GENESIS OF DEPOSITS. 

The data presented in the previous portions of this chapter are 
sufficient to indicate in a general way the most probable mode of 
origin of the ores of the district. To fully work out their genesis 
would require detailed underground studies of all the mines, accom- 
panied by extensive analyses and assays of the wall rocks, gangues, 
and ores ; such only as would have been possible, had the mines been 
open to inspection. Notwithstanding this lack of detailed infor- 
mation, it may be useful to make the best of the information that is 
available and to construct at least a probable or working hypothesis. 

SOLUTIONS. 

The ores of the district have been deposited from solutions. The 
primary ores, or those which have not been altered since their origi- 
nal deposition, are pyrite, chalcopyrite, galena, sphalerite, gold, and 
argentite or native silver. Of the gangue minerals, only quartz and 
probably siderite are apparently primary. Such rare occurrences 
as pyromorphite, stolzite, orthoclase, and wavellite are not considered 
in the discussion. Of the ore minerals, anglesite, cerussite, chal- 
cocite, malachite, and tenorite are secondary ; and of the gangue min- 
erals, actinolite, calcite, chlorite, hematite, limonite were in all like- 
lihood formed after the period of ore deposition. Of the two silver 
minerals argentite and native silver, the former is probably the pri- 
mary silver ore, from which the native silver has been derived by 
reduction; though both may be present among the primary con- 
stituents. 

The solutions, therefore, probably carried silica in large amounts, 
together with small quantities of pyrite, chalcopyrite, galena, sphaler- 



ORES AND MINES OF THE DISTRICT. 125 

ite, gold, and argentite; or more strictly, the proper elements, un- 
doubtedly with others also, such as would react to form the six afore- 
mentioned compounds. 

Becker 1 has shown that silica, gold, pyrite, and the sulphides of 
copper, zinc, and iron are soluble in waters containing carbonates 
and sulphides of the alkalies. Galena has been demonstrated to be 
soluble in water and in solutions of sodium sulphide. 2 Silver is 
probably soluble in carbonated waters. 3 It seems, therefore, that 
the primary ores of the district could have been carried in solution 
and deposited by waters containing alkaline carbonates and sulphides. 

SOURCE OF MATERIALS. 

The source of the solvent and its burden of dissolved substances 
can not be definitely established. Either the material, which has 
been concentrated to form mineralized zones and veins, has been 
brought in from outside the slate series; or it has been derived by 
circulating ground waters from this formation itself. The follow- 
ing facts are opposed to the latter view: all the rocks have been 
highly mineralized, if not by valuable metals, at least by pyrite and 
pyrrhotite; many of the formations have had large amounts of 
silica deposited in them, and none have been depleted of this com- 
pound; quartz veins are abundant, evidencing a. further amount of 
silica seemingly in excess of what the rocks themselves could have 
furnished. It seems highly probable, then, that material has been 
brought in from an extraneous source. But from where ? Pre- 
sumably from the rocks which underlie and adjoin the region. 

A few miles west from the Cid district occur areas of coarse- 
grained igneous rocks, covering many hundred square miles. It has 
been, seen (page 93) that these are later intrusive into the slate 
formation, and are composed of masses of granitic, dioritic, and 
other igneous rocks, which are themselves separate intrusions. 
Among the igneous rocks are found dikes of gabbro intermediate in 
age between diorite and granite; in the slate series gabbro also 
occurs as dikes. While it is not intended to correlate the two occur- 
rences as the result of the same intrusion, it is probable that gabbro 
was introduced into the Cid district during the general period of 

iBecker, G. F. Gold fields of the Southern Appalachians. U. S. Geol. Survey, 16th Ann. Eeport, 

P ' 2Min.°pet. Mitth., v. 11 (1890): 319 (Cf. Clarke, F. W. The data of Geo-chemistry, U. S. G. S., Bull. 
330 (1903): 585). 

Clarke, F. W. The data of Geo-chemistry. U. S. G. S., Bull. 330 (1908): 559. 



126 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

intrusive igneous activity. But whether this be accepted or not. 
the gabbro dikes are certainly indicative of a large mass of igneous 
rock at some distance, from the size of the dikes perhaps not very 
great, below the district. 

There is little or no doubt, then, that at some time following the for- 
mation and mashing of the slate series, the district was undermined 
by a mass of igneous rock. Erosion has planed down sufficiently 
near this mass to expose its offshoots which were insinuated into the 
overlying rocks in the form of gabbro dikes. It is known that there 
was a period of batholithic intrusion into the Piedmont Plateau, 
during which many hundred cubic miles of igneous rocks were 
brought so near the surface that planation has now exposed great 
areas to view. There is no reason to consider the gabbro dikes of the 
Cid district an independent phenomenon; there is some evidence 
and it is simpler to consider these a related expression of this period 
of dominant intrusion. 

Given then, a highly silicified and mineralized region, underlain 
and bordered by batholithic intrusions ; and both mineralization and 
intrusion having clearly taken place between two definite limits 
(i. e., the development of schistosity and the introduction of diabase 
dikes), it becomes very probable that the source of the solutions and 
material was predominantly magmatic. It is believed that water or 
water vapor, .excluded from the cooling igneous masses during a long 
period, was of such a nature as to carry in solution the various ele- 
ments and compounds, also contributed by the igneous rocks, which 
were precipitated in their present position to form silica, pyrite, 
chalcopyrite, galena, sphalerite, gold, argentite, and perhaps . other 
compounds. 

It is not known to what proportional extent, if any, the materials 
were contributed by the gabbro or by the large granitic masses. 
From the great amount of silica introduced, and from the acid char- 
acter of the gangues, it seems likely that the granite was the dominant 
source. Yet it is by no means impossible, and is indeed probable, 
that the gabbro also added to the mineral content of the region. 

Why so much lead and zinc were deposited at the Silver Hill, 
Silver Valley, and related mines can not be definitely stated. This 
is an important question, for these mines are distinctive in character 
and different from all other mines in the slate belt. Apparently con- 
ditions before deposition were the same ; for the country rock and 



ORES AND MINES OF THE DISTRICT. 



127 



structure are not essentially different from what is found at many 
other mines which contain very little or no galena and blende. 
Three suggestions occur to the writer, which might serve to explain 
the preponderance of lead and zinc in the mines of the Silver Hill 
type; but these are merely suggestions. (1) The solution carried 
small amounts of lead and zinc. Conditions were such in certain 
mines as to strain out and deposit these in abundance in the form 
of sulphides. This is strengthened by the fact that such deposits 
appear to be replacement deposits. Deposits of auriferous pyrite 
and chalcopyrite, on the other hand, lacked conditions necessary for 
the precipitation of galena and blende present in the solutions. (2) 
The lead and zinc deposits might be nearer the source of the mate- 
rial than deposits of auriferous pyrite and chalcopyrite. Thus ga- 
lena and sphalerite are deposited first and near the source, together 
with some chalcopyrite and pyrite. The solutions, impoverished of 
lead and zinc, deposited at greater distances only the auriferous sul- 
phides of iron and copper. This hypothesis is strengthened by the 
fact that in the Silver Hill Mine occur "dike" rocks, whose relations 
have never been accurately described, which may represent contact 
metamorphic effects and indicate proximity to an igneous mass. 
(3) A point of difference between the mines of Davidson County 
and mines in other parts of the slate belt is the occurrence of gabbro 
in the neighborhood of the former. This suggests that a slight vari- 
ation in the general magma, which was the source of the material, 
gave rise to a special type of ore deposit, rich in lead and zinc. In 
other words, the gabbro gave off solutions containing mostly lead and 
zinc, whereas the acid igneous rocks contributed chiefly auriferous 
pyrite and chalcopyrite. 

DEPOSITION OE THE ORES. 

The manner in which the ores were deposited is an important 
question. Lack of detailed and exact information concerning the 
underground features necessitates that its treatment be brief and 
largely hypothetical. 

If the ore-bearing solutions were of magmatic origin, they were 
undoubtedly at high temperatures and under great pressure at the 
outset. These would tend to work their way upward into regions 
of less temperature and pressure, and in so doing would gather into 
trunk channels of major circulation ; though whenever a porous for- 



128 THE CTD MINING DISTEICT OF DAVIDSON COUNTY. 

mation was met it is reasonable to suppose that this would act like 
a sponge and become saturated with the silica-bearing waters. Ac- 
cordingly the first effect of the mineralizing period was probably the 
addition of silica to the rock formations, resulting in the high silicifi- 
cation of the region. This may have been accompanied by the wide- 
spread impregnation of rocks with pyrite and pyrrhotite. 

The silicification of the country rocks would itself effect a change 
in circulation, and tend to direct the solutions into definite channels, 
following cleavage planes or joint directions. The more massive 
rocks at the outset were probably rendered practically impervious to 
circulation; so that the most vigorous circulation was subsequently 
confined to the schistose rocks. These, indeed, by virtue of their 
vertical structures, would tend to direct solutions into definite paths, 
in the same way in which they controlled the introduction of the 
gabbro dikes. With this restriction of the field of circulation, the 
concentration of the rarer components of the solutions was rendered 
easier ; and through a decrease in temperature and pressure, a chemi- 
cal, mechanical, and catalytic action of the wall rock, and by chemi- 
cal reactions with solutions of a different nature or from other 
sources, the formation of mineralized zones became possible. How- 
ever this may be, it is a fact that practically all the ore deposits are 
confined to schistose or mashed rocks (i. e., to the limbs of the 
folds). 

It must be remembered that the details given in the two preceding 
paragraphs are entirely suppositional, and are based upon the fur- 
ther assumption of magmatic origin. 

A few words may be added as to the probable mode of formation 
of the four types of "veins" : impregnations, stringer leads, cross 
veins, and replacement deposits. Formerly it was thought that all 
true veins were fissure veins, occasioned by the filling of gaping fis- 
sures. Recently it has been recognized that growing crystals exert 
an enormous pressure, 1 and that the pre-existence of fissures is not 
essential to the formation of veins. It would seem, therefore, that 
the impregnations and in part the stringer leads might readily be 
explained by the supposition that the vein material, entering along 
narrow seams, made a place for itself by the expansion due to crystal 
growth. This of course is not intended to preclude the possibility of 
the region having been slightly shattered previous to the mineral iza- 

iBecker, G. F., and Day, A. L. The linear force of growing crystals. Wash. Acad. Sci., Proc, 
v. 7 (1905): 283-288. . 



OKES AND MINES OF THE DISTRICT. 129 

tion; but it does render unnecessary the conception that great open 
fissures and imbricating lenticular spaces were formed at the right 
moment and remained open to receive their filling of vein matter, 
It is also quite probable that the cross veins represent the filling of 
joint planes, where circulation has been unusually vigorous and suffi- 
cient to push aside the walls to make room for continuous deposition. 
The so-called replacement deposits are of a different order, and do 
not necessarily imply pre-existing fissures. Why solutions carrying 
galena and sphalerite formed veins of a different type from solutions 
which only deposited auriferous pyrite and chalcopyrite can not 
be stated. 

AGE OF THE ORE DEPOSITS. 

The age of the ore deposits can be definitely stated to be Pre- 
Triassic. The period of deposition was certainly subsequent to the 
time of folding, and in all probability followed the igneous intru- 
sion of granite and other rocks. Since the slate series was deposited 
in Pre-Cambrian, or possibly early Paleozoic, and underwent pro- 
found changes before subjected to mineralization, it is probable that 
the period of ore deposition was included in the Paleozoic. 

SECONDARY ENRICHMENT. 

Since their original deposition, the ore deposits have undergone 
some degree of alteration near the surface, so as to form in the 
upper workings of the mines ores of a different kind from those 
found in the lower levels. These changes are of the greatest im- 
portance in the mines* of the Silver Hill type. This subject has an 
important practical bearing; from lack of definite information, it 
can be treated only in a general way. 

Surface waters, carrying oxygen and carbonic acid, attack the 
outcrops and upper parts of veins. The sulphide ores are oxidized 
to sulphates, which in turn may be changed to carbonates or oxides. 
Sulphuric acid and acid salts, formed during the process, assist in 
further decomposing the ores. The sulphates and other compounds 
differ in solubility; a separation of the more soluble from the less 
soluble takes place. The more soluble components are taken into 
solution by the surface waters and carried down into the vein, where 
below water level the conditions are such that they are precipitated. 
Thus, in general, a vein has three parts or zones: an upper or 
oxidized zone, from which the more soluble components have been 
leached; a middle or enriched zone, to which the material derived 
from the upper zone has been added ; and a lower or unaltered zone, 



130 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

extending usually to an unknown depth, which has suffered no change 
since its formation. 

The Silver Hill mine is the only mine in which the process de- 
scribed above has been of great moment. In the upper workings of 
this mine large bodies of carbonate ores (chiefly lead carbonate carry- 
ing native silver) have been found. These were formed from the 
original complex mixture of galena and sphalerite with chalcopyrite, 
silver, and gold. By a difference in solubility of the oxidized pro- 
ducts of these compounds, the zinc and copper largely disappeared 
from the upper parts of the vein ; leaving behind a mass of aurifer- 
ous and argentiferous cerussite, with subordinate amounts of the 
oxidized compounds of zinc and copper. The writer can not state 
how definite this upper oxidized zone is, or to what depth it extends. 
Previous descriptions make no attempt to discuss secondary enrich- 
ment in this mine. Probably, however, it reaches to the depth of 
about 200 feet. Below this zone occur the undecomposed sulphides. 
These have doubtless been enriched by the material dissolved from 
the zone above, but not to any appreciable extent except by the 
additions of copper and zinc sulphides. Hence the middle "en- 
riched" zone has been enriched by the less valuable components of the 
ore ; so from a practical standpoint, it is probable that the value of 
the ores below the level of the carbonates will continue with but little 
change to great depths. The vein has probably not been enriched 
by lead, silver, or gold. 

In veins of the Emmons and Conrad Hill types, it is not believed 
that secondary enrichment is important from an economic stand- 
point. Near the surface the ores are chiefly limonite, carrying free 
gold; but sulphides are found at no great depth. The surface ores 
are of course caused by the oxidation of the iron salts to limonite, 
which, with gold, is almost insoluble. 

To what degree, if any, the veins have been progressively enriched 
from their upper extents which have been eroded away, the writer 
sees no way of determining. This has an important bearing as to 
the depth to which workable ores may be expected to extend. It is 
likely, however, that the values encountered at the depths of several 
hundred feet may be found at much greater depths. 

The problem, then, of successfully mining the ores of the slate 
belt is one that can be solved by careful and economical working, 
and proper concentrating and milling of low grade ores, whose values 
seem pretty well established. 



CHAPTER VII. 

SUMMARY. 
ROCKS. 

The Cid mining district herein described comprises about 125 
square miles of Davidson County, North Carolina. Situated in the 
central portion of the Piedmont Plateau, it is a part of a great series 
of volcano-sedimentary rocks, known as the Carolina Slate Belt. 
The district includes areas of slate, acid tuff, acid volcanic breccia, 
rhyolite, dacite, andesitic tuffs and breccias, andesite, and dikes of 
gabbro and diabase. All the rocks, save the last two, range from a 
massive to a schistose condition, with sericite and greenstone schists 
as the final result of the extreme mashing respectively of the acid 
and basic rocks. 

The slate is a fine-grained, bluish to greenish rock, composed of 
varying admixtures of land waste and volcanic ash. It has a wide- 
spread extent, forming broad belts of country extending in a north- 
east direction and alternating with bands of the other rocks. 

Interbedded with the slate are found beds of rhyolitic and dacitic 
tuffs, which vary in size from narrow intercalations to broad belts a 
mile or so in width. Some of the tuff is so fine grained that its 
fragmental nature only becomes apparent under the microscope. A 
part of this has been highly silicified, forming a dense, cherty rock, 
locally called "gun-flint." The acid fine tuff grades on the one hand 
into the slate ; and on the other, into a coarser f acies, the acid coarse 
tuff, in which angular rock fragments and broken phenocrysts can 
be plainly seen with the unaided eye. Much of the acid tuff is 
chistose, and near the Silver Hill Mine a broad belt of this rock 
has been converted into an area of sericite schists. 

The acid volcanic breccia is a very coarse phase of the acid tuff, 
with a preponderance of fragments over groundmass. It occurs in 
a broad band extending the length of the area mapped and including 
Flat Swamp Ridge. With this rock are associated flows of rhyolite; 
and there is such an intimate gradation between the two as to sug- 
gest that a part of the breccia is a phase of the rhyolite brecciated 
through flowage. The rhyolite is a fine-grained, porphyritic rock, 
devitrified since its consolidation, and in favorable places exhibits 



132 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

unmistakable signs of its extrusive origin. Its best development is 
along the crest of Flat Swamp Mountain. 

Dacite comprises Kemp Mountain in the northern part of the dis- 
trict, and resembles in appearance the rhyolite. It forms an area of 
oval outline, representing the exposed portion of a surface flow. 

Corresponding to the acid series of tuffs, breccias, and flows and 
interbeddecl with them, occur a basic series of analogous volcanic 
rocks of an andesitic character. The anclesitic tuffs and breccias 
include dark green rocks, composed of visible fragments of various 
kinds and sizes, and there are both massive and schistose phases of 
these rocks. They are found passing into greenstone schists as the 
final result of dynamic metamorphism. These basic fragmental 
rocks occur widely distributed, both in long, narrow strips and in 
larger areas of oval and irregular outline. 

Andesite is of limited extent, and is represented by both an 
amygdaloidal and massive phase. It is a dark green, heavy, tough 
rock, and certain occurrences have a trachytic stamp. 

Dikes of gabbro and diabase are abundantly distributed, cutting 
the other formations. Many of the gabbro dikes are several hun- 
dred yards wide and extend for miles. These have been controlled 
in direction by the dip of the schistosity planes in the rocks into 
which they have been introduced. The diabase is of Triassic age 
and cuts all other formations, including the gabbro. 

STRUCTURE. 

Three lines of evidence ; namely, the relation of schistose to mas- 
sive formations, the nature of the bedding planes so far as pre- 
served, and the surface shapes of the formations; agree in sug- 
gesting that the district is made up of large inclined folds, with 
axial planes dipping steeply to the northwest. The present surface 
bevels this folded series, exposing the edges and folded tops of 
numerous intercalations of sedimentary and igneous rocks. Flat 
Swamp Ridge is considered the trough of a syncline, which extends 
with the ridge in a northeast direction: the two corresponding anti- 
clines on either side are also included within the district; the one 
passing to the east of Fairmont and Silver Hill, and the other in- 
cluding Denton and Kemp Mountain.' 

A great overthrust fault probably extends along the eastern edge 
of Flat Swamp Ridge, which has cut out the succession of beds 



SUMMARY. 133 

appearing on its western slope. Other minor faults possibly exist 
in the region. The schistosity, jointing, and faulting are believed 
to be largely the result of the compression which squeezed the region 
into folds. 

ECONOMIC GEOLOGY. 

The district includes the Silver Hill, Conrad Hill, Silver Valley, 
Emmons, Cid, Peters, and Ward mines; with numerous smaller 
workings and prospects. With the exception of the Gold Hill Mine, 
the Silver Hill Mine has been more extensively worked than any 
other mine in the State. 

The mines and prospects may be divided into three types, accord- 
ing to the nature of the ores: (1) The Silver Hill type, in which the 
ores consist of a complex mixture of galena and sphalerite, together 
with pyrite and chalcopyrite, the whole carrying silver and gold; 
(2) the Conrad Hill type, in which the ores consist of auriferous 
pyrite and chalcopyrite, in a gangue of quartz, siderite, and hema- 
tite; and (3) the Emmons type, in which the ores consist of aurifer- 
ous pyrite and chalcopyrite in a quartzose gangue, or as narrow 
stringers in the schists with little or no gangue. 

The "veins" may be grouped into four classes: impregnations of 
ore in the schists; stringer leads, ranging from intricating stringers 
and lenses of quartz to well-defined quartz veins, and agreeing in 
trend with the schistosity or cutting that structure at small angles ; 
cross veins, or well-defined quartz veins, which cut the schistosity at 
large angles and are usually barren; and replacement deposits, or 
zones carrying seams and lenses of ore, chiefly argentiferous and 
auriferous galena and sphalerite, in an extremely metamorphosed or 
highly silicified country rock. 

The ore deposits are believed to be of magmatic origin. The 
great mass of igneous rock which came to place near the district, as 
indicated by the igneous belt a few miles to the west and the presence 
of large gabbro dikes within the district, is competent to contribute 
solutions carrying the silica and ores, with which the region has been 
impregnated. 



APPENDIX. 

BIBLIOGRAPHY OF THE CID MINING DISTRICT. 

Ayres, Stephen 

A desription of the region in North Carolina where gold has been found. 
Med. Repos. v., 10 (1807): 148-151. 

Balch, William Ralston 

Mines and mining interests of North Carolina in 1882. 

(In his Mines, miners, and mining interests of the United States in 1882. 
pp. 6; 57-58; 61; 120-127; 1102-1105). 

Becker, George Ferdinand 

Gold fields of the Southern Appalachians. 

(In U. S. Geol. Survey, 16th Ann. Rept., pt. 3. 1895). 

Beckwith, John 

A memoir on the natural walls or solid dikes in the state of North Carolina. 
Am. Jour. Sci., Ser. I, v. 5 (1822) : 1-7. 

Blake, William Phipps 

Silver glance from North Carolina. 

Min. Mag., Ser. II, v. 1 (1860): 480. 
Silver Hill mine of North Carolina. 

(In his Silver ores and silver mines. New Haven. 1861. pp. 67-68). 

Booth, James Curtis 

Analyses of various ores of lead, silver, copper, zinc, iron, etc., from King's 
mine, Davidson County, North Carolina. 
Am. Jour. Sci., Ser. I, v. 41 (1841) : 348-352. 

Boyd, Charles Rufus 

Conrad Hill, N. C, gold and copper mines. 
The Virginias, v. 3 (1882): 176. 

Campbell, H. D., & Brown, W. G. 

Composition of certain mesozoic igneous rocks of Virginia. 
Geol. Soc. Am., Bull, v. 2 (1891): 339-347. 

Cobb, Collier 

A new Paleotrochis locality, with some, notes on the nature of Paleotrochis. 
Elis. Mit. Sci. Soc, Jour., v. 20 (1904): 11-12. 

Cooper, Thomas 

Floetz trap in North Carolina. 

Am. Jour. Sci., Ser. I, v. 4 (1822): 241. 

Diller, Joseph Silas 
Origin of Paleotrochis. 

Elis. Mit. Sci. Soc, Jour., v. 16 (1899): 59-67. 



136 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Eaton, Amos 

The gold of the Carolinas in talcose slate. 

Am. Jour. Sci., Ser. I, v. 18 (1830): 50-52. 

Eaton, Harry Nelson 

Micro-structure and probable origin of flint-like slate near Chapel Hill, North 
Carolina. 
Elis. Mit. Sci. Soc, Jour., v. 24 (1908): 1-8. 

Emmons, Ebenezer 

American geology, containing a statement of the principles of the science, with 
full illustrations of the characteristic American fossils. 
Albany. Sprague & Co. 1855. 
Geological report of the midland counties of North Carolina. 

N. C. Geol. Survey. 1856. 
On new fossil corals from North Carolina. 

Am. Jour. Sci., Ser. il, v. 22 (1856): 389-390. 

Genth, Frederick Augustus 

Contributions to mineralogy. 

Am. Jour. Sci., Ser. II, v. 16 (1853): 81-86. 

Am. Jour. Sci., Ser. II, v. 19 (1855) : 15-23. 

Am. Jour. Sci., Ser. II, v. 45 (1868): 305-321. 
Minerals of North Carolina. 

(Appendix c to Kerr, W. C, Rept. Geol. Survey of North Carolina. Ra- 
leigh, 1875). 
On the mineral resources of North Carolina. 

Frank. Inst. Jour., v. 63 (1872): 48-61; 114-130. 
The minerals of North Carolina. 

U. S. Geol. Survey. Bull. 74. 1891. 

Gold and silver produced by the mines of America from 1492-1848. 
Min. Mag., Ser. I, v. 1 (1853): 365-373. 

Gold mines in North Carolina. 

Am. Jour. Sci., Ser. I, v. 16 (1829): 360-363. 

Graton, Lewis Caryl 

A reconnaissance oi some gold and tin deposits of the Southern Appalachians 
U. S. Geol. Survey. Bull. 293 (1906). 

Hall, James 

An account of a supposed artificial wall discovered under the surface of the 
earth in North Carolina. In a letter to James Woodhouse (and Dr. Wood- 
house's reply). 

Med. Repos., v. 2 (1799): 272-278. 

Hanna, George Byron 

Mines of the Appalachian ranges. 

Sch. of Mines Quart., v. 3 (1882): 208-211. 






BIBLIOGRAPHY. 



137 



Hidden, William Earle 

A new meteoric iron from North Carolina. 

Am. Jour. Sci, Ser. Ill, v. 20 (1880): 324-326. 

Hitz, John 

To the president and directors of the Washington Mining Company. 

Hodge, James T. 

The boulders and deposit gold mines of North Carolina. 

Assoc. Am. Geol. and Nat., Repts. of 1st, 2d, and 3d meet. (1841) : 34-35. 

Hunt, Thomas Sterry 

A historical account of the taconic question in geology, with a discussion of the 
relations of the taconic series to the older crystalline rocks. 
Roy. Soc. Can., Trans., v. I, Sec. 4 (1883): 217-270, v. 2, Sec. 4. (1884): 
125-157. 

Jackson, Charles Thomas 

Report on the Conrad Hill gold mine, Davidson County, North Carolina. 
Min. Mag., Ser. I, v. 2 (1854): 190-191. 

Johnson, Walter Rogers 

Some observations on the gold formations of Maryland, Virginia, and North 
Carolina. 
Am. Assoc. Adv. Sci., Proc, 4th meet. (1850): 20-21. 

Kerr, W. C, and Hanna, G. B. 

Ores of North Carolina: being chapter II of the second volume of the geology 
of North Carolina. 

N. C. Geol. Survey. Raleigh (1888). 

Kerr, Washington Caruthers 

Report of the Geological Survey of North Carolina. 

1875. 
Some peculiarities in the occurrence of gold in North Carolina. 
Am. Inst. Min. Eng., Trans., v. 10 (1882) : 475-476. 

Kerr, W. C, and Genth, F. A. 

The minerals and mineral localities of North Carolina: being chapter I of the 
second volume of the geology of North Carolina. 
N. C. Geol. Survey, Raleigh (1881). 

Kunz, Georce Frederick 

Native silver in North Carolina. 

Am. Jour. Sci., Ser. IV, v. 7 (1899): 242-243. 

Laney, Francis Baker 

The Gold Hill mining district of North Carolina. 

N. C. Geological and Economic Survey, Bull. 21, 1910. 
A Thesis. Yale University (1908). 



138 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Laney, F. B., and Pogue, J. E., Jr. 

An outcrop map of the Virgilina copper district. Scale 1 : 24003. 
N. C. Geol. Survey (1908). 

Lyon, Edward West 

The Progress of gold mining in North Carolina. 
Eng. and Mg. Jour., v. 87 (1909): 293-297. 

Leeds, Stephen P. 

Gold ores and their workings. 

Min. Mag., Ser. I, v. 7 (1856): 23-32; 265-275; 344-358; 445-453. 
Notes on the gold regions of North and South Carolina. 
Min. Mag., Ser. I, v. 2 (1854) : 27-34; 357-399. 

Leidy, Joseph 

Remarks on Paleotrochis. 

Acad. Nat. Sci. Phil., Proc, v. 1 (1859) : 150. 

Lewis, Zechariah 

Remarks on a subterranean wall in North Carolina. 

Med. Repos., v. 4 (1801): 227-234. 
Letters on a subterranean wall in North Carolina. 

Med. Repos., v. 5 (1802) : 397-407. 

LlNDGREN, WALDEMAR 

Orthoclase as gangue material in a fissure vein. 
Am. Jour. Sci., Ser. IV, v. 5 (1898): 418-420. 

Marsh, Othniel Charles 

On the Paleotrochis of Emmons from North Carolina. 
Am. Jour. Sci., Ser. II, v. 45 (1869): 217-219. 

Mitchell, Elisha 

Elements of geology; with an outline of the geology of North Carolina. 1842. 
On the geology of the gold region of North Carolina. 

Am. Jour. Sci, Ser. I, v. 16 [1829] : 1-19. 
Report on the geology of North Carolina, conducted under Board of Agriculture. 
Pt. 3. Raleigh (1827). 

Moore, Frederick 

Gold in North Carolina. 

Sci. Am. Suppl, v. 53 (1902): 218-219. 

Nitze, Henry Benjamin Charles 

Gold Mining in the Southern States. 
Engineering, v. 10 (1896): 821-844. 

Some late views on the so-called taconic and huronian rocks of North Carolina. 

Elis. Mit. Sci. Soc, Jour, v. 13 (1896): 53-72. 
The genesis of the gold ores in the central slate belt of the Carolinas. 

Eng. and Mg. Jour, v. 63 (1897): 628-629. 



BIBLIOGRAPHY. 139 

NlTZE, H. B. C, AND Hanna, G. B. 
Gold deposits of North Carolina. 

N. C. Geol. Survey, Bull. 3 (1898). 

NlTZE, H. B. C, AND WlLKINS, H. A. J. 

Gold mining in North Carolina and adjacent South Appalachian regions. 

N. C. Geol. Survey, Bull. 10 (1837). 
The present condition of gold mining in the Southern Appalachian states. 
Am. Inst. Min. Eng., Trans., v. 25 (1895) : 651-795. 

Olmsted, Denison 

On the gold mines of North Carolina. 

Am. Jour. Sci., Ser. I, v. 9 (1825): 5-15. 
Report on the geology of North Carolina, conducted under the Board of Agri- 
culture. Raleigh (1825-27). 
Paleotrochis of Emmons. 

Am. Jour. Sci., Ser. II, v. 23 (1857) : 278. 
Am. Jour. Sci., Ser. II, v. 24 (1857): 151. 

Petherick, Thomas 

Report upon the Silver Hill mine, Davidson County, North Carolina. 
In Report of the Silver Hill Mining Co., New York (1860): 8-11. 
Pogue, Joseph E., Jr. 

Geology and structure of the ancient volcanic rocks of Davidson County, 
North Carolina. 

Am. Jour. Sci., Ser. IV, v. 28 (1909): 218-238. 
On Olivine-diabase from Davidson County, North Carolina. 
Proc. U. S. Nat. Museum, v. 37 (1910): 475-484. 

Pratt, Joseph Hyde 

Mining industry in North Carolina during 1900 (also 1901, 1902, 1903, 1904, 
1905, 1906). 
N. C. Geol. Survey. Econ. Papers No. 6, 7, 8, 9, 11, 14, 15. 
Pratt, J. H., and Steel, A. A. 

Recent changes in gold mining in North Carolina. 

In Mining industry in North Carolina during 1906. N. C. Geol. Survey, 
Econ. Paper No. 14: 19-82. 
Report of the Director of the Mint upon the statistics of the production of 
the precious metals in the United States. 
Washington (1880-1904). 

Robinson, Samuel 

Catalogue of minerals from North Carolina. 

In his Catalogue of American minerals with their localities. Boston (1825) : 
210-220. 

Rogers, Henry Darwin 

Classification of the metamorphic strata of the Atlantic slope of the middle 
and southern states. 

Bost. Soc. Nat. Hist., Proc, v. 6 (1859): 140-145. 

Rothe, Charles E. 

Remarks on the gold mines of North Carolina. 
Am. Jour. Sci., Ser. I, v. 13 (1828) : 201-217. 



140 THE CID MINING DISTRICT OF DAVIDSON COUNTY. 

Taylor, Richard Cowling. 

Report on the Washington silver mine, Davidson County, North Carolina. 
1845. 

Tenny, William J. 

The Conrad Hill mine, Davidson County, North Carolina. 

Min. Mag., Ser. I, v. 1 (1853): 628. 
The Silver Hill mine, North Carolina. 

Min. Mag., Ser. II, v. 1 (1860): 368-371. 

Van Hise, Charles Richard. 
Archaean and Algonkian. 

U. S. Geol. Survey, Bull. 86 (1892). 

Watson, Thomas Leonard. 

Copper-bearing rocks of Virgilina copper district, Virginia and North Carolina. 
Geol. Soc. Am., Bull. v. 13 (1902): 353-376. 

Weed, Walter Harvey. 

Copper deposits of the Appalachian States. 

U. S. Geol. Survey, Bull. 213 (1902). 
Notes on the Carolina gold deposits. 

Eng. and Mg. Jour., v. 72 (1901): 494. 
Types of copper deposits in the southern United States. 

Am. Inst. Mg. Eng., Trans., v. 30 (1900): 449-504. 

Weed, W. BL, and Watson, T. L. 

Th? Virginia copper deposits. 

Econ. Geol., v. 1 (1903): 309-330. 

Whits, Charles Henry 

An examination into the nature of Paleotrochis. 
Elis. Mit. Sci. Soc, Jour., v. 11 (1894): 50-66. 

Whitney, Josiah Dwtght 

The metallic wealth of the United States described and compared with other 
countries. Philadelphia (1854). 

Williams, George Huntington 

Ancient volcanic rocks along the eastern border of North America. 

Am. Geol., v. 13 (1894): 212-213. 
The distribution of ancient volcanic rocks along the eastern border of North 
America (with map). 

Jour. Geol., v. 2 (1894): 1-31. 

Woodhouse, James 

Remarks on a letter of the Rev. Zechariah Lewis relating to a subterranean 
wall discovered in North Carolina. 
Med. Repos., v. 5 (1802): 21-24. 
Additional observations on the subterranean minerals near the Yadkin in 
North Carolina. 

Med. Repos., v. 7 (1804): 26-27. 



PUBLICATIONS 



North Carolina Geological and Economic Survey. 



BULLETINS. 

1. Iron Ores of North Carolina, by Henry B. C. Nitze, 1893. 8°, 239 pp., 20 
pi., and map. Postage 10 cents. 

2. Building and Ornamental Stones in North Carolina, by T. L. Watson and 
F. B. Laney in collaboration with George P. Merrill, 1906. 8°, 283 pp., 32 pi., 
2 figs. Postage 25 cents. Cloth-bound copy 30 cents extra. 

3. Gold Deposits in North Carolina, by Henry B. C. Nitze and George B. Hanna, 

1896. 8°, 196 pp., 14 pi., and map. Out of print. 

4. Road Material and Road Construction in North Carolina, by J. A. Holmes 
and William Cain, 1893. 8°, 88 pp. Out of print. 

5. The Forests, Forest Lands and Forest Products of Eastern North Carolina, 
by W. W. Ashe, 1894. 8°, 128 pp., 5 pi. Postage 5 cents. 

6. The Timber Trees of North Carolina, by Gifford Pinchot and W. W. Ashe, 

1897. 8°, 227 pp., 22 pi. Postage 10 cents. 

7. Forest Fires: Their Destructive Work, Causes and Prevention, by W. W. 
Ashe, 1895. 8°, 66 pp., 1 pi. Postage 5 cents. 

8. Water-powers in North Carolina, by George F. Swain, Joseph A. Holmes 
and E. W. Myers, 1899. 8°, 362 pp., 16 pi. Postage 16 cents. 

9. Monazite and Monazite Deposits in North Carolina, by Henry B. C. Nitze, 
1895. 8°, 47 pp., 5 pi. Postage 4 cents. 

10. Gold Mining in North Carolina and other Appalachian States, by Henry 
B. C. Nitze and A. J. Wilkins, 1897. 8°, 164 pp., 10 pi. Postage 10 cents. 

11. Corundum and the Basic Magnesian Rocks of Western North Carolina, by 
J. Volney Lewis, 1895. 8°, 107 pp., 6 pi. Postage J/ cents. 

12. History of the Gems Found in North Carolina, by George Frederick Kunz, 
1907. 8°, 60 pp., 15 pi. Postage 8 cents. Cloth-bound copy SO cents extra. 

13. Clay Deposits and Clay Industries in North Carolina, by Heinrich Ries, 
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14. The Cultivation of the Diamond-back Terrapin, by R. E. Coker, 1906. 
8°, 67 pp., 23 pi., 2 figs. Postage 6 cents. 

15. Experiments in Oyster Culture in Pamlico Sound, North Carolina, by 
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10. Shade Trees for Ncrth Carolina, by W. W. Ashe, 1908. 8°, 74 pp., 10 pi., 
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17. Terracing of Farm Lands, by W. W. Ashe, 1908. 8°, 38 pp., 6 pi., 2 figs. 
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18. Bibliography of North Carolina Geology, Mineralogy and Geography, with 
a list of Maps, by Francis Baker Laney and Katherine Hill Wood, 1909. 8°, 
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19. The Tin Deposits of the Carolinas, by Joseph Hyde Pratt and Douglass B. 
Sterrett, 1905. 8°, 64 pp., 8 figs. Postage 4 cents. 



142 PUBLICATIONS N\ C. GEOLOGICAL AND ECONOMIC SURVEY. 

20. Water-powers of North Carolina: An Appendix to Bulletin 8. In Press. 

21. The Gold Hill Mining District of North Carolina, by Francis Baker Laney 
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22. A Report on the Cid Mining District, Davidson County, N. C, by J. E. 
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ECONOMIC PAPERS. 

1. The Maple-Sugar Industry in Western North Carolina, by W. W. Ashe, 1897. 
8°, 34 pp. Postage 2 cents. 

2. Recent Road Legislation in North Carolina, by J. A. Holmes. Out of print. 

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4. The Mining Industry in North Carolina During 1900, by Joseph Hyde Pratt, 

1901. 8°, 36 pp., and map. Postage 2 cents. 

?- Takes up in some detail Occurrences of Gold, Silver, Lead and Zinc, Copper, Iron, Manganese, Co- 
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Building Stones, and Coal in North Carolina. 

5. Road Laws of North Carolina, by J. A. Holmes. Out of print. 

6. The Mining Industry in North Carolina During 1901, by Joseph Hyde Pratt, 

1902. 8°, 102 pp. Postage 4 cents. 

Gives a List of Minerals found in North Carolina; describes the Treatment of Sulphuret Gold Ores, 
giving Localities; takes up tne Occurrence of Copper in tne Virgilina, Gold Hill, and Ore Knob districts; 
give3 Occurrence and Uses of Corundum; a List of Garnets, describing Localities; the Occurrence, 
Associated Minerals, Use3 and Localities of Mica; the Occurrence of North Carolina Feldspar, with 
Analyses; an extended description of Nortn Carolina Gems and Gem Minerals; Occurrences of Mona- 
zite, Barytes, Ocner; describes and gives Occurrences of Graphite and Coal; describes and gives Occur- 
rences of Building Stones, including Limestone; describes and gives Uses for the various forms of Clay; 
and under tne head of Otner Economic Minerals" describes and gives Occurrences of Chromite, Asbes- 
tos, and Zircon. 

7. Mining Industry in North Carolina During 1902, by Joseph Hyde Pratt, 

1903. 8°, 27 pp. Postage 2 cents. 

8. The Mining Industry in North Carolina During 1903, by Joseph Hyde Pratt, 

1904. 8°, 74 pp. Postage 4 cents. 

Gives descriptions of Mines worked for Gold in 1903; descriptions of Properties worked for Copper 
during 1903, togetner with assay of ore from Twin-Edwards Mine; Analyses of Limonite ore from Wilson 
Mine; the Occurrence of Tin; in some detail the Occurrences of Abrasives; Occurrences of Monazite 
and Zircon; Occurrences and Varities of Graphite, giving Methods of Cleaning; Occurrences of Marble 
and other f orms of Limestone; Analyses of Kaolin from Barber Creek, Jackson County, North Carolina. 

9. The Mining Industry in North Carolina During 1904, by Joseph Hyde Pratt, 

1905. 8°, 95 pp. Postage 4 cents. 

*■" Gives Mines Producing Gold and Silver during 1903 and 1901 and Sources of the Gold Produced during 
1901; describes the mineral Chromite, giving Analyses of Selected Samples of Chromite from Mines in 
Yancey County; describes Commercial Varieties of Mica, giving the manner in which it occurs in North 
Carolina, Percentage of Mica in the Dikes, Methods of Mining, Associated Minerals, Localities, Uses; 
describes the mineral Barytes, giving Method of Cleaning and Preparing Barytes for Market; describes 
the use of Monazite as used in connection with the Preparation of the Bunsen Burner, and goes into the 
U3e of Zircon in connection with the Nernst Lamp, giving a List of the Principal Yttrium Minerals; 
describes the minerals containing Corundum Gems, Hiddenite and Other Gem Minerals, and gives New 
Occurrences of these Gems; describes the mineral Graphite and gives new Uses for same. 

10. Oyster Culture in North Carolina, by Robert E. Coker, 1905. 8°, 39 pp. 
Postage 2 cents. 

11. The Mining Industry in North Carolina During 1905, by Joseph Hyde 
Pratt, 1906. 8°, 95 pp. Postage 4 cents. 



PUBLICATIONS N. Q. GEOLOGICAL AND ECONOMIC SURVEY. 143 

Describes the mineral Cobalt and the principal minerals that contain Cobalt; Corundum Localities; 
Monazite and Zircon in considerable detail, giving Analyses of Thorianite; describes I ant alum Miner- 
als and gives description of the Tantalum Lamp; gives brief description of Peat Deposits; the manu- 
facture Sf Sand-lime Brick; Operations of Concentrating Plant in Black Sand Investigations; gives 
Laws relating to Mines, Coal Mines, Mining, Mineral interest in Land, Phosphate Rock, Marl Beds. 

12. Investigations Relative to the Shad Fisheries of North Carolina, by John 
N. Cobb, 1906. 8°, 74 pp., 8 maps. Postage 6 cents. 

13. Report of Committee on Fisheries in North Carolina. Compiled by Joseph 
Hyde Pratt, 1906. 8°, 78 pp. Postage k cents. 

14. The Mining Industry in North Carolina During 1906, by Joseph Hyde 
Pratt, 1907. 8°, 144 pp., 20 pi., and 5 figs. Postage 10 cents. 

Under the head of "Recent Changes in Gold Mining in North Carolina," gives methods of mining, 
describing Log Washers, Square Sets, Cyanide Plants, etc., and detailed descriptions of Gold Deposits 
and Mines are given; Copper Deposits of Swain County are described; Mica Deposits of Western North 
Carolina are described, giving Distribution and General Character, General Geology, Occurrence, 
Associated Minerals, Mining and Treatment of Mica, Origin, together with a description of many of the 
mines- Monazite is taken up in considerable detail as to Location and Occurrence, Geology, including 
Classes of Rocks, Age, Associations, Weathering, method of Mining and Cleaning, description of Mona- 
zite in origina Matrix. 

15. The Mining Industry in North Carolina During 1907, by Joseph Hyde Pratt, 
1908. 8°, 176 pp., 13 pi., and 4 figs. Postage 15 cents. 

Takes up in detail the Copper of the Gold Hill Copper District; a description of the Uses of Monazite 
and its associated Minerals; descriptions of Ruby, Emerald, Beryl, Hiddenite, and Amethyst Localities; 
a detailed description with Analyses of the Principal Mineral Springs of North Carolina; a description 
of the Peat Formations in North Carolina, together with a detailed account of the Uses of Peat and the 
Results of an Experiment Conducted by the United States Geological Survey on Peat from Elizabeth 
City, North Carolina. 

16. Report of Convention called by Governor R. B. Glenn to Investigate the 
Fishing Industries in North Carolina, compiled by Joseph Hyde Pratt, State 
Geologist, 1908. 8°, 45 pp. Postage k cents. 

17. Proceedings of Drainage Convention held at New Bern, North Carolina, 
September 9, 1908. Compiled by Joseph Hyde Pratt, 1908. 8°, 94 pp. Postage 
5 cents. 

18. Proceedings of Second Annual Drainage Convention held at New Bern, 
North Carolina, November 11 and 12, 1909, compiled by Joseph Hyde Pratt, and 
containing North Carolina Drainage Law, 1909. 8°, 50 pp. Postage 3 cents. 

19. Forest Fires in North Carolina During 1909, by J. S. Holmes, Forester, 
1910. 8°, 52 pp., pi. Postage 5 cents. 

20. Wood-using Industries of North Carolina, by Roger E. Simmons, under the 
direction of J. S. Holmes and H. S. Sackett, 1910. 8°, 74 pp., 6 pi. Postage 
7 cents. 

VOLUMES. 

Vol. I. Corundum and the Basic Magnesium Rocks in Western North Carolina, 
by Joseph Hyde Pratt and J. Volney Lewis, 1905. 8°, 464 pp., 44 pi., 35 figs. 
Postage 32 cents. Cloth-bound' copy 30 cents extra. 

Vol. II. Fishes of North Carolina, by H. M. Smith, 1907. 8°, 453 pp., 21 pi., 
188 figs. Postage 30 cents. 
' Vol. III. The Physiography and Geography of the Coastal Plain Region of 
North Carolina. In Press. 



Samples of any mineral found in the State may be sent to the office of the 
Geological and Economic Survey for identification, and the same will be classified 



144 PUBLICATIONS N. C GEOLOGICAL AND ECONOMIC SURVEY. 

free of charge. It must be understood, however, that no assays, or quantita- 
tive determinations, will be made. Samples should be in a lump form, if 
possible, and marked plainly on outside of package with name of sender, post- 
office address, etc.; a letter should accompany sample and stamp should be en- 
closed for reply. 



These publications are mailed to libraries and to individuals who may desire 
information on any of the special subjects named, free of charge, except that in 
each case applicants for the reports should forward the amount of postage 
needed, as indicated above, for mailing the bulletins desired, to the State Geolo- 
gist, Chapel Hill, N. G. 



DETE CAROLINA LIBRARY 

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